I have an ancient spare PC that I’m determined to keep going, just for the sport of it, without spending much money. If it dies it dies and there’s little to lose. That’s why I dare to poke around in the bowels of the machine, in the bios and the registry and other mysterious places---the do it yourself geek thing. Here’s a video I found helpful from the How Stuff Works series.
Be very, very careful when you do this.