first unplug the muse and keyboard from the computer than try to restart the computer .
after that shutdown the computer and connect the mouse and keyboard in the computer .
restart the computer , if it wil create a probelm than restart the computer in safe mode.
go to start>programs>accessories>system tools>restore .
restore the computer to its previous date .
so all the settings back and the computer will run in normal mode
for further assistance you can approach at this source at
http://www.iyogi.co.uk/microsoft-windows-xp-su pport.html