SSRQ, forgive me for forgetting about this when I replied to your post on the LucasForums, but both of you can give the MSI installer package found @ http://www.markusegger.at a try. It was primarily written with users of Windows XP and Vista 64-bit version in mind, but if you have 32-bit Vista, it should work better for you than the installer that comes on the CD. You might want to uninstall your copies of XvT (backing up your .plt files, of course) before trying this because the MSI installer will prompt for the XvT disk, installing that game alongside BoP.
I'll make this blunt and quick. When i try to install Balance Of Power the installer crashes and tells me (Direct copy) "The decompression of %s failed, There may not be enough space available in the TEMP directory.
XvT itself installs fine, as do Tie Fighter and X-Wing