I've done a bit of research into this today - it appears that LDS used to distribute "Folio Viewer" software as the browser for their Census and Vital Records Index CD's. See Mark Howell's article at
http://www.oz.net/~markhow/writing/more.htm. An article on Wikipedia at
http://en.wikipedia.org/wiki/Folio_Corporation shows how this product was sold from company to company over the years and probably explains why LDS did not upgrade beyond v4.2. It seems from
http://www.nextpage.com/news/releases/pr_061704.htm that even Version 4.5 was compatible only with Windows 2003 and Windows ME. A later article at
http://www.cedion.de/fast_sheets/FAST_Folio_Publisher_Product_Sheet.pdf shows that version 4.6 runs on a 64-bit platform, although it does not mention Vista or Windows 7. I'm guessing that this version would be likely to run OK on 64-bit Windows 7 and probably requires the 64-bit version.
Bad news is that according to
http://groups.google.com/group/soc.genealogy.britain/browse_thread/thread/8184af4b5a19f7e3?tvc=2 this version 4.6 of Folio Views cost £140 in 2006. It's since been replaced by version 4.7 which might be the proper Windows Vista/Windows 7 version but as a business tool no doubt costs even more!
Even if the alternative of the XP compatibility mode did work it would mean for me as a user of Windows 7 Home Premium a cost of £100 to upgrade to Home Professional in order to be able to use the XP Mode!
It occurs to me that the LDS software might run under WINE - the Windows emulator for Linux. Since I'm running Linux under Sun's Virtual box on my 64-bit Windows 7 PC - specifically Ubuntu 9.10 - this might be a free way of getting compatibility for older versions of Windows for nothing!
Richard