When you say "shut down" do you mean it shuts down completely? When the computer hibernates, it's designed to essentially "shut down" until you do something, like type a key, to wake it back up.
It sounds as if your computer is blue screening, as known as the Blue Screen of Death (BSOD). It would be very helpful if we could see the error codes that appear on the screen. Follow these instructions to keep the computer from rebooting when it blue screens: click Start, type sysdm.cpl in the search box and hit enter, under the Advanced tab click Settings under Startup and Recovery, uncheck the box Automatically restart under System Failure and then click OK. Take note of the error codes and messages that appear on the screen and post them back here.
Here's a guide on how to handle BSODs if you're inclinded to do some troubleshooting on your own -- http://support.microsoft.com/kb/958233.
When i say shut down, i mean it shuts down completely. I know that if hibernated, just pressing a button can bring it back alive. But it shuts down completely that i have to press the power button again and start whatever i was doing earlier all over again. Iv bin able to get what the instructions are whenever it shows the blue screen. It says;
"A problem has been detected and windows has been shut down to prevent damage to your computer.
If this is the first time you've seen this stop error screen, restart your computer. If this screen appears again, follow these steps;
Check to make sure any new hardware or software is properly installed.
If this is a new installation, ask your hardware or software manufacturer for any windows update you might need.
If problems continue, disable or remove any newly installed hardware or software. Disable BIOS memory options such as caching or shadowing,
If you need to use safe mode to remove or disable components, restart your computer, press F8 to select advanced startup options, and then select safe mode.
*** STOP : 0x0000009F ( 0X0000000000000003, 0XFFFFFA8005849060
Collecting data for crash dump...
Initializing disk for crash dump...
Beginning dump of physical memory...
Dumping physical memory to disk...100.
That above message is what is shown at that moment it shows the blue screen. Ill appreciate if you can tell me how to go from there. Thank you.