Corrupt file in windows, can't start my computer. Help?

The last thing I did on my computer was update McAfee, my internet security software, and it needed to be restarted. When I restarted it, I got an error screen (not the blue screen of death, one of the black ones :P) saying that WINDOWS\SYSTEM32\CONFIG\SYSTEM was corrupt or missing. Now my desktop won't work (I'm on my laptop right now) Help, someone? please?

If you can help, answer. If you can walk me through this step by step which would be awesome, email me at fetabaguette@hotmail.com with your yahoo ID so we can talk over chat. Again, I would really be very appreciative if anyone could help me out here.

Corrupt file in windows, can't start my computer. help?free antivirus

re-install windows

Corrupt file in windows, can't start my computer. help?internet

If you haven't done anything since you posted this question, see if you can go back a step with system restore.

Power on

As soon as you see the system checking memory and before Windows tries to load, press and continue to hold the F8 key. You will come to a black and white DOS menu. Click F3 for Safe Mode.

%26gt;%26gt;%26gt;Once in Safe Mode, click Start, Help.

%26gt;%26gt;%26gt;On my computer, with WinXP, if I click Start, Help, I come to a screen where one of the choices is system restore. If your computer works this way, you can return to where you were before you updated McAfee.