I have been experiencing some problems with my home PC. It was showing me problems with hard drives. First I though that my hard drives are quite old and need replacement. I got myself new SATA drives since my motherboard supports both PATA and SATA, but then the problem continued and what I have found out is that my power supply was dieing. New SATA drives are faster and probably consume some more power :(. Anyway, I got myself a new 400W power supply and now everything works just perfect.
I also thought to get myself a new PC, but then I remembered that a Quad Core is coming very soon and decided to wait for it :)