Hi,
Please post your system specs using this as a guide:
http://www.techsupportforum.com/558208-post1.html
If it is rebooting then I am thinking it is a driver issue. If we know the error message, we can track down the exact cause. Follow the steps
here under Recovery Settings and continue with your normal activities. This time, though, instead of rebooting, you should see a blue screen. Be sure to post the technical details on the blue screen including the STOP error.