The width of the product list in the buynow module is ultimately driven by the available width of the pane you add it to in your skin.  Here are a couple items you can try in your skin that will increase the width of the product listing:
 
    - Increase the width on the outer table or div of your skin 
 
    - Increase the width of the pane that you add the buynow module to
 
 
Here is the code from the productlist.ascx page on our site I think the only thing that we changed was the "col width" statements on the table in the datalist highlighted in yellow below:
<%@ control language="C#" autoeventwireup="true" inherits="Smith.DNN.Modules.BuyNow.ProductsList, App_Web_productslist.ascx.54f2e0e1" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>
<link href="module.css" rel="stylesheet" type="text/css" />
<table runat="server" id="tbMain" visible="true" width="100%">
    <tr>
        <td >
            <asp:Label ID="lblSearchLabel" runat="server" Text="Search:"/> 
            <asp:DropDownList ID="ddlSearch" runat="server"/>
            <asp:DropDownList ID="ddlSort" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlSort_SelectedIndexChanged" >
                <asp:ListItem Value="MyDefault" Text="-Select-"  />
                <asp:ListItem Value="HighToLow" Text="Price High to Low" />
                <asp:ListItem Value="LowToHigh" Text="Price Low to High" />
                <asp:ListItem Value="BrandAZ" Text="Brand A-Z" />
                <asp:ListItem Value="BrandZA" Text="Brand Z-A" />
                <asp:ListItem Value="SkuAZ" Text="Sku A-Z" />
                <asp:ListItem Value="SkuZA" Text="Sku Z-A" />
                <asp:ListItem Value="NewArrivals" Text="New Arrivals" />
                <asp:ListItem Value="Featured" Text="Featured" />
            </asp:DropDownList>
        </td>
        <%--<td width="5px"> </td>--%>
        <td>
            <asp:TextBox ID="txtSearch" runat="server" Width="175px"/> 
            <asp:Button ID="btnSearch" runat="server" Text="Go" OnClick="btnSearch_Click" />        
            <asp:Label ID="lblRecordsLabel" runat="server" Text="Records:"/>  
            <asp:DropDownList ID="ddlRecords" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlRecords_SelectedIndexChanged">
                <asp:ListItem>10</asp:ListItem>
                <asp:ListItem>20</asp:ListItem>
                <asp:ListItem>50</asp:ListItem>
                <asp:ListItem>100</asp:ListItem>
            </asp:DropDownList>
        </td>
    </tr>
    <tr style="height:20"><td></td></tr>
</table>
<table runat="server" id="tbMain1">
    <tr>
        <td valign="top" runat="server" id="tdMenuCategories"> <asp:Menu ID="MenuCategories" runat="server" OnMenuItemClick="MenuCategories_MenuItemClick"
             BorderColor="GradientActiveCaption" BackColor="White" BorderWidth="1px" Width="107px" Height="151px" BorderStyle="None"></asp:Menu>  
        </td>
        <td style="text-align: center; vertical-align: top;" runat="server" id="tdProductList">
            <asp:DataList ID="dtProductslist" runat="server" Width="100%" RepeatColumns="1" RepeatDirection="Horizontal"
                EnableViewState="False" OnItemCreated="dtProductslist_ItemCreated" OnItemDataBound="dtProductslist_ItemDataBound">
                <ItemTemplate>
                    <table cellspacing="1" cellpadding="5" border="0" width="100%">
                        <col width="1%" />
                        <col width="20%" />
                        <col width="45%" />
                        <col width="3%" />
                        <col width="15%" />
                        <col width="2%" />
                        <col width="12%" />
                        <tr>
                            <td></td>
                            <td valign="top" align="left">
                                <table>
                                    <tr runat="server" id="trThumb">
                                        <td style="text-align:center; width:100%;" >
                                            <a href='<%# EditUrl("ProductID",((int)DataBinder.Eval(Container.DataItem,"ProductID")).ToString(),"ProductDetails",DataBinder.Eval(Container.DataItem,"SEOURL").ToString()) %>' >
                                                <img alt='' style="vertical-align: top; border-width: 0; text-align: center; clip: auto; padding: 1px; position: relative;" runat="server" id="img" src="" /></a>
                                        </td>
                                    </tr>
                                    <%--Multi column fields--%>
                                    <tr>
                                        <td style="text-align:center; width:100%;">
                                            <asp:LinkButton ID="hylink2" Text='<%# DataBinder.Eval(Container.DataItem, "ModelName") %>' runat="server" CssClass="SmithProdText" OnClick="btnProductLink_Click" />
                                            <%--<asp:HyperLink ID="hylink2" Text='<%# DataBinder.Eval(Container.DataItem, "ModelName") %>' runat="server" CssClass="SmithProdText"
                                            NavigateUrl='<%# EditUrl("ProductID",((int)DataBinder.Eval(Container.DataItem,"ProductID")).ToString(),"ProductDetails",DataBinder.Eval(Container.DataItem,"SEOURL").ToString()) %>' /> --%>
                                            <asp:Label runat="server" ID="lblSummary2" Text='<%# DataBinder.Eval(Container.DataItem, "Summary") %>' Visible="false" CssClass="SmithProdText"/>
                                        </td>
                                    </tr>
                                    
                                    <tr>
                                        <td style="text-align:center; width:100%;" class="SmithProdText" nowrap>
                                            <asp:Label runat="server"  ID="lblPriceLabel2" Text="Price:" />
                                            <asp:Label runat="server" ID="lblPrice2" />
                                            <asp:TextBox runat="server" ID="txtPrice2" Width="50px" MaxLength="5" />
                                        </td>
                                    </tr>
                                    <tr>
                                        <td style="text-align:center; width:100%;">
                                            <asp:ImageButton ID="ibAddToCart2" runat="server" OnClick="btnAddBasket_Click" ImageUrl="~/DesktopModules/Smith.BuyNow/images/add_to_cart2.gif" />
                                            <asp:ImageButton ID="ibSelect2" runat="server" OnClick="btnSelect_Click" ImageUrl="~/DesktopModules/Smith.BuyNow/images/options.gif" Visible="false" />
                                        </td>
                                    </tr>
                                </table>
                            </td>
                            
                             <%--Single column fields--%>
                            <td valign="middle" align="left" width="200">
                                <table>
                                    <tr >
                                        <td><asp:Label runat="server" ID="lblProductSKULabel" Text="SKU: " Visible="false" style="float:left; text-align:left; width:50px;"/>
                                        <asp:Label runat="server" ID="lblProductSKU" Text='<%# DataBinder.Eval(Container.DataItem, "ModelNumber") %>' Visible="false" style="float:left; text-align:left;"/>
                                        </td>
                                    </tr>
                                    
                                    <tr>
                                        <td>
                                            <asp:HyperLink ID="hylink" Text='<%# DataBinder.Eval(Container.DataItem, "ModelName") %>' runat="server" CssClass="SmithProdText"
                                            NavigateUrl='<%# EditUrl("ProductID",((int)DataBinder.Eval(Container.DataItem,"ProductID")).ToString(),"ProductDetails",DataBinder.Eval(Container.DataItem,"SEOURL").ToString()) %>' />
                                            <asp:Label runat="server" ID="lblSummary1" Text='<%# "<br>" + DataBinder.Eval(Container.DataItem, "Summary").ToString() %>' Visible="false" CssClass="SmithProdText"/>
                                        </td>
                                    </tr>
                                </table>
                                
                            </td>
                            <td></td>
                            
                            <td valign="middle" align="left" width="150px" class="SmithProdText">
                                <table>
                                    <tr>
                                        <td><asp:Label runat="server"  ID="lblPriceLabel" Text="Price:" CssClass="SmithProdText" /> </td>
                                        <td>
                                            <asp:Label runat="server" ID="lblPrice" CssClass="SmithProdText"/>
                                            <asp:TextBox runat="server" ID="txtPrice" Width="50px" MaxLength="5" /> 
                                        </td>
                                    </tr>
                                    
                                    <tr>
                                        <td><asp:Label runat="server" ID="lblMemberPriceLabel" Text="Member Price:" Visible="false" CssClass="SmithProdText"/></td>
                                        <td><asp:Label runat="server" ID="lblMemberPrice" Visible="false" CssClass="SmithProdText"/></td>
                                    </tr>
                              
                                    <tr>
                                        <td><asp:Label runat="server" ID="lblQty" Text="Qty:" CssClass="SmithProdText"/></td>
                                        <td><asp:TextBox ID="txtQuantity" Width="50px" MaxLength="4" CssClass="SmithProdText" runat="server" Text="1"/></td>
                                    </tr>                                    
                                </table>                                
                            </td>
                            <td></td>
                            <td align="center">
                                <asp:ImageButton ID="ibAddToCart" runat="server" OnClick="btnAddBasket_Click" ImageUrl="~/DesktopModules/Smith.BuyNow/images/add_to_cart2.gif" />
                                <asp:ImageButton ID="ibSelect" runat="server" OnClick="btnSelect_Click" ImageUrl="~/DesktopModules/Smith.BuyNow/images/options.gif" Visible="false" />
                            </td>
                        </tr>
                        <tr>
                            <td>
                                <asp:HiddenField ID="hndProductID" Value='<%# DataBinder.Eval(Container.DataItem, "ProductID") %>' runat="server" Visible="false" />
                                <asp:HiddenField ID="hndSEOURL" Value='<%# DataBinder.Eval(Container.DataItem, "SEOURL") %>' runat="server" Visible="false" />
                            </td>
                        </tr>
                        <tr style="height:20"><td></td></tr>
                    </table>
                </ItemTemplate>
            </asp:DataList>
        </td>
    </tr>
    <tr style="height:20"><td></td></tr>
    <tr>
        <td colspan="3" align="center">
            <asp:Label ID="lblResult1" runat="server"></asp:Label> 
            <asp:Label ID="Label2" runat="server"></asp:Label>
            <asp:ImageButton ID="IbAddtoCart" runat="server" ImageUrl="~/DesktopModules/Smith.BuyNow/Images/viewcartorange_btn.gif" OnClick="IbAddtoCart_Click" />
        </td>
    </tr>
    <tr style="height:20"><td></td></tr>
    <tr>
        <td align="center" colspan="3">
            <asp:LinkButton ID="LBFirst" runat="server" OnClick="LBFirst_Click">First</asp:LinkButton> 
            <asp:LinkButton ID="LBPrev" runat="server" OnClick="LBPrev_Click">Prev</asp:LinkButton> 
            <asp:Label ID="lblResult" runat="server"></asp:Label> 
            <asp:LinkButton ID="LBNext" runat="server" OnClick="LBNext_Click">Next</asp:LinkButton> 
            <asp:LinkButton ID="LBLast" runat="server" OnClick="LBLast_Click">Last</asp:LinkButton>
        </td>
    </tr>
</table>