Hi!
I have to say something before I give you a solution... You should never ever go into the system32 folder much less replace anything, not unless you're an IT professional... Do you have a Windows disc? If so, do a repair install of Windows, all this will do is fix the critical Windows files that have been corrupted....
1) Put the Windows CD in the CD drive. Make sure that you go into the BIOS and check the boot order to be certain it is set to boot from the CD drive and not the Hard Drive, you can usually access the BIOS by tapping the delete key or the escape key.... If you give me the exact type of motherboard you have I can try and find out what key you press to get to the BIOS...
2) You will be shown and screen of options... Hit Enter, this will take you to the Windows License Agreement
3) Accept the agreement
4) The computer will search for Windows Installs that are already there..
5) Select the one you want the computer to repair, the most recent one would be the best and if there is only one just pick that one......
6) Press R once you have highlighted the install of Windows you want it to repair...
7) Critical files will be copied to the hard drive and your computer will power down and reboot... DO NOT press any key to boot from the CD when given the option... Just let it do it's own thing and when it is finished your apps. and settings will still be the same....
You will LOSE files.... If this is not for a Windows XP machine let me know as the instructions will become different....
Hope This Helps!