my comptor keeps crashing out right out sometimes and back to desktop other times .even more when i try to play toca race driver 2 please help

Any error messages?

To get some change these settings:

You can turn off the feature that instructs XP to autostart on system
failure. Right click on My Computer and select Properties->Advanced
Tab->Startup & Recovery section->Settings button->uncheck "Automatically
restart" Apply. This will give you a blue screen with info on it and you
will have to manually restart the computer. The info might give you an idea
whether or not the problem is hardware or software related.

Also go to Start > Run > (type in) eventvwr.msc

Look under System & Application tabs for red X's that coincide with shutdown & post all messages in full.