eMachine keeps restarting

I have a friend's PC I'm trying to get running,He said that their power went out and that when they tried to start the PC it would get to emachine screen then would restart.
I pulled out cmos batt. and set bios to defaults. It will now go to the Windows screen then says window is starting up.Then you here a click,and it restarts.I put the hard drive in my PC as slave and it seems fine.Any ideas, I'm thinking motherboard but hope not. Thanks for any ideas in advance, Chuck It's a T2958 512 ram

 

If there any system diagnostics CD run that CD on a startup boot making sure the CD starts first and post the results here to the forum and we will help.

 

We took off automatic restart .This is the error that we got when it shut down.
STOP:c000021a{Fatal System Error}
The windows logon Process system process terminated unexpectedly with a ststus of 0xc0000005 (0x00000000 0x00000000).
The system has been shut down.

 

Try reseating the RAM or replacing it completely.

 

I changed slots & tryed another stick from a PC thats running. No go.Forgot to tell ya all that Chuck.

 

Got it going I did a complete reinstall Chuck Thanks for all replys.