Clicking hard drive due to power supply?

I have an Asrock P4i48 motherboard with 1 Seagate 250 GB hard drive, 768 MB ram, 256 MB EVGA video card, Pentium 4 2.80 Ghz cpu 800 Mhz bus, Hercules 400 watt pwr supply, 1 dvd rom, 1 dvd-rw. Recently I have been having issues with clicking hard drives that will freeze up and give me the blue screen of death in win xp. I have used ide and sata but both seem to have issues. I have noticed also the light on my mouse and the num key light on the keyboard will flicker. I have lowered the speed of my cpu to 1.6 Ghz and it seems to get rid of the clicking. Could the pwr supply be going out? Thanks.