Windows XP logon problems

When I start my computer it gets to the logon screen, then when I try to logon it says cause a error in explorer.exe and when I try to run it in the task manager I get the same thing. I tried using Safe Mode, but it does the same thing. I dont know what to do, I can use the Windows Recovery Console. I dont want to have to reinstall Windows XP.

PS: It happened the first time I restarted after installing SP2.

 

I have tried /p what does /r do?

 

Okay, A new problem has occured. I did that and I lost my CD-Key, so now I am stuck on the enter CD-Key page. I tried using my friends key but it didnt work. And when I go to the Recovery console it now says invalid password but before the installation it worked. So now when i restart the computer it just keeps going into the installation.

 

I didnt set up my computer so I dont know if Windows was already on it or I used a Disc, But I have a Windows Professional Disc. But the CD-Key wont work on it.

 

Yes I do know how to use the regestry, but I cant get into Windows besides the logon page. I tried using his CD + Key but it said wrong CD Key, i will try to fix the Key if its wrong.

PS: It is completely legal to use his CDKey and CD since I already payed for it, same as if you have lost the Key, you already payed for it so its not illegal.

 

Problem solved, CD-Key was wrong. Thank you for all your help Tim.

 

hmmmm, I used my Windows XP on the computer but now it gives me the startup thingies that say its counterfeit. Which Windows update is this?