my computer keeps rebooting itself, abit of a pain when your in the middle of
a program.
You are presumably blue-screening, and you are set to the default of
rebooting whenever that happens. Right-click My Computer, and choose
Properties. On the Advanced tab, click Settings under Startup and
Recovery. Under System failure, uncheck the box "Automatically
restart.
Now when the problem occurs again, instead of restarting, you will get
the blue screen with diagnostic information. Post back with those
details for more help.
By the way, this is very often a hardware problem (overheating, power
supply issues, or flaky RAM) rather than a Windows one.