Why is my PC rebooting alone ???

[karapuz]

I just don't understand why my PC reboots like this ! A couple of days ago I had a rootkit but I could clean it but I still cannot run the safe mode of my Windows and rebooting appears at the most inappropriate moments. Is there anything to be done

[karapuz]

What's more... I thought of reinstalling my Windows but somehow it finds errors while installing, so I can't do it... Although the CD has been used before and is perfectly clean... Isn't that strange ?

[mauserme]

Sometimes reboots can happen because of heat build up and sometimes because of malware.  Did this problem occur prior to the rootkit infection?  Are there any other signs if infection?

Try scanning with the free version of AVG Antispyware

http://free.grisoft.com/doc/20/lng/us/tpl/v5

To boot into safe mode, see if this works

> Click Start, Run, then type MSCONFIG in the box and click OK
> The System Configuration Utility appears, On the BOOT.INI tab, Check the "/SAFEBOOT" option, and then click OK and Restart your computer when prompted.
> When you're finished open MSCONFIG again, on the BOOT.INI tab,  uncheck "/SAFEBOOT" and click OK to restart your computer

[Lisandro]

Sometimes this happens due to overheat (check your fans).
Sometimes, drivers conflict, see recent thread related to that http://forum.avast.com/index.php?topic=25979.msg212325#msg212325