Windows 7 Freezes After User Screen?

I'm using Windows 7 32 bits, and had no trouble till yesterday. For a year and so, always update and have no problem. But last update made computer go crazy.It did no turn off by herself, it took more than half an hour, so I turned it off pressing power button. After that, when booting, it shows users screen, enter pass and it freezes in the "welcome" screen, with the little think turning arround forever.So far, tried with safe mode. Thing is, VERY weird, it never happened beforme to me, even on XP, there is NO chance of a previous good cofiguration. So, when I try to go back to previous state of those beautiful updates, I cannot, for there is no chance. I don't know why, seems like it was turned off. When xp user, had so many time system back that way.

Also tryed changing to "backup" files of SYSTEM and SOFTWARE, in :WINDOWSSYSTEM32CONFIGREGBACK I don't know if doing it right, apparently not =P copied back files from that directory in system32config and restarted, but same thing happens.I am using the same machine to post this, with another HD, so I think that it's no hard problem, otherwise, I wouldn't be able to use it. Runs games and stuff, so it's OK I guess.Also tryed, before, CHKDISK and defrag.Now I have the "good" disk, from where I boot, and the other connected, and can access to old Windows, and disk itself, so, I guess too that the HD works fine.