my computer restart automatically,please tell me what is problem.i check every thing,just need a help.Download BlueScreenView:
http://www.nirsoft.net/utils/blue_screen_view.html
unzip downloaded file and double click on BlueScreenView.exe to RUN the program.
when scanning is done, go to EDIT - Select All
Go to FILE - SAVE Selected Items, and save the report as BSOD.txt
Open BSOD.txt in Notepad, copy all of the content, and paste it into your next replyAlso to note that if your system is set up for automatic updates, and it was not turned on on Tuesday to TAKE the weeky updates, it may have performed updates on its own and rebooted.

Symptoms of this would be a warning that system is going to reboot in 10 minutes ETC, you can postpone or if your not there to answer the system will reboot on its own even if you have something important running.

HOWEVER if you were in the middle of something and it just reboots, the tool that allan suggested may show helpful info, however if you have a QUICK power dip that caused the reboot sometimes your system will reboot without any bsod info.