Assuming you're using Windows XP, 1936, right-click on the My Computer icon on your desktop and choose Properties from the menu. Click the Advanced tab, then click the Settings button in the "Startup and Recovery" section. In the "System Failure" section, untick the "Automatically Restart" option, click OK, Apply and OK to exit. Now when your computer encounters the same problem again, rather than shutting down, it will give an error message. Post that error message here.