Weird automatic shutdown

Hi, I'm just using my laptop just like what I do everyday, but today, it's acting really weird. At first, it's slow so I restarted it, but it was still the same so again, I restarted it. But this time, when it reached the login screen, it suddenly shuted down. I thought it was just overheating, but when I turned it on again the same thing happened. I only reached up to the login screen.

Things I already done to troubleshoot:
-run into Safe Mode(unsuccessful, just shuts down)
-start repair tool 3 times(unsuccessful)
-system restore from different dates(unsuccessful - there's an error in restoring)
-memory diagnostic(nothing really happened here)


What should I do next? Thanks a lot for your answers!

Run a full scan with your anti-virus suite. Since no AV is 100% effective 100% of the time I'd also run a couple of free on-demand scans. These are recommended:

Malwarebytes

ESET Online Scanner

If any malware is detected please post back for additional scanning/removal instructions.

If no malware is detected I would next check for damaged or corrupt system files by running a system file checker scan from an elevated command prompt (option two.) If any problems are found, run the scan 3 times and reboot the computer after each scan.

SFC /SCANNOW Command - System File Checker

Hi. Thanks for your response. How could I run a scan if I coudn't pass in the login screen?

There is no error in sfc /scannow. What could be the problem?

You may have to boot from either the Windows 7 installation DVD to access repair options or from some other "live" disk like Ubuntu, Hiren's BootCD, Ultimate Boot CD, etc. If you don't have a Windows 7 install DVD you can obtain a free, legal copy from Digital River (an official Microsoft download site.) You'll need to download the ISO file of the version of Windows 7 that came with your computer, save it to desktop, then burn it to disk.

Official Windows 7 SP1 ISO from Digital River « My Digital Life

Home | Ubuntu

Hiren's BootCD 15.2 - All in one Bootable CD » www.hiren.info

Ultimate Boot CD - Overview

You might also want to go through these troubleshooting guides prepared by one of the Forum experts.

Troubleshooting Windows 7 Failure to Boot

Troubleshooting Windows 7 Failure to Boot

You could also try using that Windows 7 install disk to do a repair install which should preserve your user accounts, data, programs, system drivers, etc.

Repair Install

All of the above suggestions are primarily related to software issues (damaged or corrupt files, malware, etc.) But if your laptop has suffered a hardware failure (CPU, motherboard, hard drive, etc) nothing will work until the bad hardware is replaced.

I think the problem is now overheat, because I managed it to boot again but when the processes are very slow I switched it to high performance then it shutted down again.