I have an old copy of Office 97 that I still use. I don't want the ribbon interface, and its more than sufficient for my needs so lets avoid the "its sooooo old" debate.
It refused to install on my Win 7 x86_64 machine despite trying all the various Win XP and Win 2k compatibility modes. In the end I finally persuaded the main install to complete, but the two patches refused to install, again despite the compatibility modes. I copied the patched exe files from my Win XP machine and it now runs fine. What a faff!
It was easier (seamless almost) to install on my MacBook Pro (Mid 2010 i7) using the Crossover Windows adaption layer than on my Win 7 machine.
I'm not going to debate the Apple backwards compatibility claim you make, but the M$ claim is bollocks!