Windows 98 Locks Up Randomnly

I have a HP Pavilion 8660C, Pentium III 533 MHz machine running Windows 98 SE. The problem is that it locks up (no mouse or keyboard input) randomly. I thought it was a IE 5.0 problem at first, because it happens frequently when online, but it also locks up in Word, when running games, and just about anytime it feels like it.

What can I do to fix this, or even to determine what it is? Is there anything I can do with HP or Microsoft to make them assist?

– Jeff