Will not boot to the welcome screen

[Nish94]

I just installed something for windows service pack 3 by mistake and an error messege showed up saying "some component have been replaced by this installation" and "installation was not succecful". Then I got the service pack 2 setup and the programe was installed and when I tried to restart my PC, it doesn't get beyond the Windows XP booting screen to the Welcome Screen, instead it turns off and start from the beginnig again. What should I do ? And what is the problem here ?

 

[Sam234]

Try booting to safe mode, see if that works.

Otherwise lookup key press to get to recovery menu for your machine, then use system restore & go back to a date when it worked.