Computer randomly restarts (sometimes crash) while using.

Where did you get the drivers from? MFG?

I agree that this is likely a driver. I would still check the system disk before going through your drivers. This is easy, just right click on the drive in windows explorer, click tools, check now, schedule disk check. Then restart and it will check the disk on the restart.
Assuming this is okay, you need to look at your system. Did you use a recovery disk from the laptop manafacturer or do you have a clean windows 7 disk? The problem most likely is either the video card or the LAN. Both of these can be hard to find drivers for since they are usually made by the laptop manafacturer, not the hardware manafacturer like AMD. I would google both devices for new drivers and download them but do not install them.
Do one at a time. Uninstall the video card in device manager and then run driver sweeper found here:
http://phyxion.net/item/driver-sweeper.html
Then install the driver first with windows, then with the latest version of the driver.
Do the same for the LAN.
If you cannot find the drivers on google, check the laptop's site for specific updates.
Hopefully you will find the problem.

ThermoDust said:

Where did you get the drivers from? MFG?

well that depends on the driver. I.E; I use Realtek HD Audio as my sound driver so I go to Realtek's website

ParkerB said:

I agree that this is likely a driver. I would still check the system disk before going through your drivers. This is easy, just right click on the drive in windows explorer, click tools, check now, schedule disk check. Then restart and it will check the disk on the restart.
Assuming this is okay, you need to look at your system. Did you use a recovery disk from the laptop manafacturer or do you have a clean windows 7 disk? The problem most likely is either the video card or the LAN. Both of these can be hard to find drivers for since they are usually made by the laptop manafacturer, not the hardware manafacturer like AMD. I would google both devices for new drivers and download them but do not install them.
Do one at a time. Uninstall the video card in device manager and then run driver sweeper found here:
http://phyxion.net/item/driver-sweeper.html
Then install the driver first with windows, then with the latest version of the driver.
Do the same for the LAN.
If you cannot find the drivers on google, check the laptop's site for specific updates.
Hopefully you will find the problem.

I already did as you instructed, but the problem still happen.
Well, until recently, my computer seems to work fine in Safe Mode but yesterday the problem happened while in safe mode. So, any suggestion what to do?

Some people said to me that it was a bad hard drive or faulty power supply or even a corrupted motherboard. How do I know which one is the one causing the problem?

@azrisam, did you ever solve this problem? Just to review, you have done a clean reinstall after formatting the drive, correct? Do you have a disk that came with your motherboard? If so did you install the drivers from the CD? Did you try going to the manafacturers website and try downloading the drivers from the site and installing them that way? If you have done this and you are still having the problem, I would replace the hard drive. That is where my money is at. I have a few spare drives if you are interested. I would send them to you for free. The only other option I have would be to clear the CMOS on your motherboard before doing the clean install but honestly I do not think it is worth the time.

If your computer has it run a memory diagnostics, this error is caused by a bad memory stick. If you want you can also try to run with only one stick in to see if it happens with it, if it does, then switch sticks and then if it stops you found your bad RAM.

I just replaced my laptops RAM and stopped having this issue. Usually if your system overheats it can cause the RAM to go bad especially if it is near the CPU.