Ran Microsoft Memory tester.
Tried more, same type memory.
Tried another Hard Drive.
Tried 4 O.S.'s - XP, 2000, ME, 98se.
Changed cabling.
Removed all unecessary hardware - Network adapter, both cdroms, modem, floppy
Windows 98se seems to be the less sensitive. XP and 2000 are hopeless...