You know there's a lot of drivers for legacy hardware for windows 7 that people took the time to develop, probably not for 64bit but 32bbit you should be pretty dandy.
Have you tried lately?
As an example, I have this chip programmer (EPROM programer) which only work on XP. And it's one of my work tools.
I tried everything on the book to make it work on Windows 7 (would be good run Windows 7 on this box but I could not make that thing work. And XP is still working fine even with some apps saying they don't want to run without .NET 4... -_-;
You see, that's the MS policy which make old OSes unusable. Every time they update the development tools and compilers they put traps on the code it generate so it "pretends" to run slower on a computer with older OS so when you upgrade you get a "false result" of the computer getting faster, more responsive.
They are very good at being jerks.
Edit: That's another very good reason (it's related to having options) people are moving to open source stuff. Intel can be jerk with their chips but with physical products it's easier to get away with it (I'm looking at you nVIDIA).