System locks up



This is on a KT7A Soyo MB,AMD Athlon 750, with 128 Dimm.
The HD is a Western Digital 40 gig and I'm running Windows 2K. Here is what happens. Anytime between bootup and 10 minutes being up, the harddisk freezes. The HD LED stays on, the screen freezes. There are no error messages on the screen. After 3-5 minutes, the system reboots by itself. It doesn't matter whether I am online or offline, it still does this. I am using a 300W Power supply. I don't know if this is HD related or what, but the HD does freeze. Also, when the vaccuum cleaner is turned on in the house, the system reboots. When i saw this, I thought it was an electrical problem. So I hooked up the system to a APC and it still did the same thing. There is a Compaq Deskpro in the house too, and it doesn't have this electrical problem. Does anyone have a clue as to what this could be? I am through with building computers. I plan to buy a laptop in 2 months and throw this system out the window.