The random rebooting of your computer is not necessarily a software problem. First though, I would ensure your virus definitions are up-to-date and I would run a full system scan. Also, make sure that ALL of your drivers are good.
If that doesn't work, check the fan on your processor. If you touch it and burn your finger, you need a new fan and that should fix the problem. I have also seen bad RAM and hard drives cause the problem. Hope that helps