Windows 7 Freezes after user screen - Updates

Hi there, and thanks to everyone!
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 C:\WINDOWS\SYSTEM32\CONFIG\REGBACK I don't know if doing it right, apparently not =P copied back files from that directory in system32\config 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.

Any suggestions? I would realy appreciate your help.

Thanks!!!

Oh! Forgot to say that I am writting now from Windows 7 ultimate x64. But really need my system back, evenmore, for I want to know how to solve it! =D
Should it be useful, Gygabyte with AMD PHENOM 4x, integrated vga-need cash for video!-, 4GB RAM.-

Greetings!

Go through the steps for Troubleshooting Windows 7 Failure to Boot and let us know if you need help as your proceed through those steps.

Also, I did not understand your original post completely. Did you try a system restore? If not, try the following:

• Read carefully through System Repair Disc - Create...
• Use the System Repair Disc to access the System Recovery Options...
• Use the System Recovery Options to choose System Restore...
• Follow OPTION TWO of System Restore and pay close attention to the NOTE: in OPTION ONE step 8.