Need help. Explorer crashes during start up!!!!!!!!!!!!!!!!!!!!!!!!!!!

I have a big problem, i was being stupid. My cousin brought his computer to my house, to see if i could get all his spyware and viruses out of his computer. So i did. In the process the programs i used deleted two files wininet.dll and SHLWAPI.dll so i though maybe i could just use the files from my computer and just put them on to his computer. For wininet.dll it worked just fine the error messages about that file disapeared. So confident i did the same for shlwapi.dll but at start up explorer.exe crashes and the computer dosent finish starting up. Ive tried deleting the shlwapi.dll that i put from my computer, using taskmanager but everytime i click on delete taskmanager crashes. I could run other programs thruw run. I tried system restore but, unfortunately i had disabled it tring to get rid of a virus using norton antivirus instructions. So all the system restore points were erased!!! i have run out of ideas. So ive decided to reinstal windows but dont know how?????? can anyone help me?????

 

Is there any way to repair or fix this problem with out reinstaling windows?

 

Thnx, but i decided to go with a fresh new instal of Xp
Ran into another small problem. Windows isnt able to detect the sound card????? The computer is a power spec from microcenter and i belive it had an ac 97' sound card? Have any idea where i could get a driver for it? Or how to instal it? Or get that thing working?

 

I went to Dxdiag and this is what it gave me for bios

Phoenix - AwardBios v6.00PG

and i also cant seem to find the key that will let me acces the bios.
uggg so many problems.

Man i appreciate ur help. Thnx alot!!

 

its a clone as u said its power spec from Microcenter. O.k then i guess im going to have to open the comp and see. It will take a while since its at my cousins house.