If you've got a clean install of the latest version open inc_header.asp and look at line 280. If not the line should look like this: " <td valign=""top"" width=""50%""><a href=""default.asp"" tabindex=""-1"">" & getCurrentIcon(strTitleImage
Edit the HREF to point to the strHomeURL: " <td valign=""top"" width=""50%""><a href=""" & strHomeURL & """ tabindex=""-1"">" & getCurrentIcon(strTitleImage
That should fix it for the title image. If you want the Home link in the nav menu to point to the same location you'll need to find that link in the sForumNavigation also in inc_header.asp and edit the link there as well.
(You're too quick for me HuwR :) )