The biggest problems caused by Windows 7 and 8 is the transition from a 32bit OS to a 64bit one ... older software written for 32bit Windows often doesn't quite work right when it finds itself installed in C:\Program Files (x86) instead of C:\Program Files
I also think the 32bit flavors of Windows 7 (is there a 32bit Win8?) don't work quite as well as they should. ESPECIALLY when installed on a 64bit machine.
This is unfortunate, but necessary. The advantages of 64bit are just too great (ability to use more than 3.5GB RAM alone).

