I browsed some websites then I shut down my PC. Later,I switched it on.it booted to winxp logo(like 2 scrolls),then restarted. I tried it severally but same thing happens. I tried to repair it, the problem persists. I reinstall winxp, the setup copied files successfully but could initialise the windows installation.It keeps restarting when winxp logo is displayed. What do I do?

How did you try to repair?

See if these steps below may help

Repair Installation
A Repair Install will replace the system files with the files on the XP CD used for the Repair Install. It will leave your applications and settings intact, but Windows updates will need to be reapplied.

Perform a Repair Installation (http://www.microsoft.com/windowsxp/using/helpandsupport/learnmore/tips/doug92.mspx)