SP -
My FSX runs in Win7 x64, as does my FS 9.1 Classic. The Classic install runs in Win XP SP3 compatibility mode, which something Win7 lets you choose.
Whatever you do, do not install either your FSX or your FS9 to C:\Program Files\ whatever. The Win7 security nuisance will cause you all sorts of grief.
I have mine in C:\FS10\ and C:\FS Classic.. That way, the files that FS updates each time you use it, are outside PF and so the Win7 UAC does not see them as system files, so UAC actually allows you to update those files on your own 'poota. UAC = User Access Control...I don't remember authorising MS to decide what files I should be allowed to update on my own computer
Apart from that sort of nonsense, I have found Win7 to be a good stable platform, as XP was. To Vista, I never went.
One thing I have found is that Win7 seems to make a complete dog's breakfast of storing files. It is a good idea to defrag before doing any big flying, or after d/l and install new planes, scenery, etc..
I use a free app from auslogics:
http://www.auslogics.com/en/software/disk-defrag/It is quick and effective, as far as I am concerned. Never mind the "improve your 'poota ' " stuff - just instal the defragger.
Hope this helps
MikeW