Comp Crash but no BSOD

[Potatocodone]

Specs:
Manufacturer: Lenovo
Model: Y430
CPU: Intel T5800
Memory: 3GB DDR2
Hdd: 250GB SATA (Western Digital)
OS: Windows XP

So my mother is having a problem with her laptop. Every time she try to log into Windows XP the computer would immediately restart. There is no BSOD or what-so-ever. I try booting into safe mode to both my mother's account and windows XP administration account but same result however a message would pop up saying "user profile could not be located" or something along the lines like that.

I have ran memtest86+ and ran Western Digital hdd test and no errors reported.

I ran PC doctor and check and test the CPU and motherboard and everything passes with flying colors.

I have pull the hard-drive out and plug it into my desktop and scan for virus and such but the hard-drive came out pretty clean. I used Symantec anti-virus, est nod32, and avg.

Even when sitting at the log-in screen for 1 min the laptop will suddenly reboot.

Anyone else got any idea before I reformat?

 

[shiarua]

Sounds like a memory and or hard drive problem (despite memtest and WD hdd tests passing)

If you can, I would try to boot into the Windows XP recovery console and run fixmbr

Does the laptop have enough power left in the battery? a faulty power supply could also be the cause (or bad caps inside the computer).