No matter what these games freeze up an restart my machine lego racers,lego harry potter,lego knights kingdom. On other systems there running fine but except the main gaming machine.
Just to make sure, it's RESTARTING your computer and not SHUTTING OFF your computer, right?
In that case, it's a suppressed Blue Screen of Death.
Do this: Start -> Control Panel -> System -> Advanced Tab -> click "Settings" under "Startup and Recovery," uncheck "Automatically Restart" -> Apply -> OK.
Fire up one of those games again.
This time, you'll get the Blue Screen of Death. Write down EVERYTHING on the Blue Screen and post it here.