What is wrong with my pc?

Your pc has been set to reboot when windows sees an error. While the computer starts, you keep tapping the F8 key to display a list of start options, select Safe Mode. After computer starts in safe mode you can enter system properties by holding "windows" key (between ctrl and alt keys) down and tap pause/ break key. Click on "advanced" tab and select startup and recovery settings. On this page there is a box for automatic restart. If there is a tick in that box you need to remove it and shut down the computer.

Doc
August 2008