A little word of advice for those who are frightened (like me) of accepting that their memory chips may be faulty.
I have had tremendous trouble with my system, bad booting, blue screens of death, STOP messages in particular 0X0000008E most searches referred to memory, finally in desperation I downloaded the Microsoft Memory Checker, created the floppy and changed the boot sequence and viola! first pass an error, left to run for 4 passes of 8 tests, error every time.
Removed the 512 chip from slot 2 again ran the checker "No Problem"
Removed the 512 chip from slot 1 replaced with the one removed from slot 2, errors every second or third pass. temporary replacement of unknown brand 256 chip. Tested for 4 hours no problem.
The original memory was Kingston???