PC restarting Problem

Hello,
Hello,

I had assembled desktop PC and i had recently formatted it and installed whatever my neeful software.
I also installed Macfee 8.5i Enterprises in it. For 3 to 4 days it worked properly. One day it started giving problem
and it was whenever i tried to shutdown my PC it gets restart again. It showed no error or message nothing.
Only it gets restart whenever i tried to shutdown it. But strange is that after restarting when it comes to the logging page from the options there is shutdown option from that shutdown option it gets shutdown properly.

Pls any one had face this problem before and go the right solution on it please reply .

I am try to reinstall windows Xp But not solve my problem.

So Help me.......