Im sure you could add a bit more info so we can try and help you ,when did it start , how are you shutting it down .with the start /shutdown option or with the Case front power on/off button
Sorry,it all started a few days ago when i installed some program that I allready uninstalled, then I run another program: Advanced Windows care v2 to clean up temp files and defrag my HD, when I try to restart the PC via the normal mode: START-TURN OFF COMPUTER-TURN OFF, it goes into saving your settings and everything but instead of turning off it just reboots again so I have to press and hold the power button to turn it off .
If not the same problem, some stunningly parallel characteristics. Under the heading of "Windows XP Shut Down and Automatic Reboot Problems", here is a statement of the problem the Microsoft Help and Support site was addressing:
"I am running Windows XP Professional and it absolutely refuses to shut down. Every time I tell it to shut down it goes through the motions, but when it gets to the point to turn off the machine, the BIOS screen comes up and the machine reboots." That is the problem I was experiencing. (How is that different from this thread?)
The straightforward solution was:
1. Right-click My Computer, and then click Properties.
2. Click the Advanced tab.
3. Under Startup and Recovery, click Settings to open the Startup and Recovery dialog box.
4. Clear the Automatically restart check box, and click OK the necessary number of times.
5. Restart your computer for the settings to take effect. At this point all you have achieved is a clean shutdown, power off, no automatic reboot. Assuming the automatic reboot happened as a result of an error in the shutdown sequence, then you still have a problem, and there could be multiple causes. But that's a different problem. The next step would be to examine the error log an learn what sent the shutdown sequence into a tailspin. Even without disabling the automatic restart, one could look at the error log and deal with the underlying issue. Probably should anyway. But if you really need to get the PC into a POWER OFF state without actually pulling the plug, the above fix should be useful.