i have installed windows Xp professional successfullly and it was running right ..but now when i start windows and click on my name an eror report comes and nothiing after that comes just a blank wallpaper comes ,,,,,,,,,,,,,,,please can u tell me that ...email me a t
pakmoon2001@Hotmail.com

OK, first off, what's the error? What are your system specs? Have you recently added new hardware or software?
Press CTL-ALT-ESC, click on the Processes tab, then click on the CPU column - is there any process that is taking an inordinate amount of processor time?

Have you tried booting from the Windows CD and selecting "Repair Windows" (although I would leave this until nothing else has worked.

Without more information, no one can help you.

AndyF