two identical computers on network turn off; power light on

two compac p4-1700 computers are both within a few hours stopping and just leaving the power light on. I have to secure power to recycle. The software is not identical, there is a there is a tird computer on the network which is fine. I have replaced the H
D in one system thinking that was the problem. I originally swapped the HDs and the problem stayed with the drive so I thought that was the problem. Once I replaced the drive and it still crashed I tried the other computer and it was also stopping. Now I h
ave swapped the drives to the original with the exception of using the new HD in the original computer. Today when accessing the second computer via the LAN it stopped. That maybe unrelated but who nows, certainly I am stumped. PS using Norton Internet Sec
urity 2003 which is updated and all three systems are windows update current. OS is XP Home 2002 SP1. Thanks for helping. Tad