Just adding my two cents here: I have/had the same problem with Win 7 Freezing up. I tried all the updating and stuff but it only seemed to make it worse. After a fair amount of following various guides and helpful suggestions from forums as this, i pretty much gave up and started contemplating going back to XP. Well, in the end i gave Win 7 one last shot, and tried to figure out what set off the freezes. I rolled back to Vanilla and only installed The SP1 update and the optional Media Center Update, after i realized that Media Player had an almost sure-fire tendency to freeze up my system. I found that this, combined with Turning Off all "Retrieve/Send Info From Internet"-Option helped a lot. So from that i deducted that Win 7 had a problem with this feature and i then started looking for other programs that did this automatically. I, like many others, use AVG Free, and when you install it, you have the option of some extra features (if you didn't choose Express Install), realizing that these features did the same thing, send/retrieve info, i de-selected them and only installed the Anti-Virus program. This helped a ton! Now Windows only lags occasionally when i use Firefox.
I have no idea, which of the Updates, beyond the ones mentioned, are safe to install. So a Trial and Error approach is all i can recommend.