There are no problems whatsoever with CS2, I have it running on two PC's, one running Win7 64bit and one Win7 32bit.
Far easier to use than it ever was under Vista.
Just install as Administrator and when installed adjust compatibility settings if you have any issues. I can't remember now.
OK, at home now and have checked CS2 on the 64bit desktop. There is no compatibility set, neither is it run as administrator.
All I did was run the setup file as admin when installing.
It runs perfectly.
Should have said a number or very ancient plugins, like KPT3, also work fine as well.
But I hardly go near it nowadays, hence still on CS2. Since Lightroom came out I don't really need anything else. If I do Elements is perfectly adequate.