- possibly RAM was removed from the A590 w/o checking the jumpers - verify them and/or try amnesia; try w/ only 512K activated
- the WD XT drives are a PITA, dog slow, noisy and unreliable - get a decent, even small SCSI drive and you'll see the difference
- check the PSU connector's solder points: they tend to tear out; if internal 5V is unreliable the 500 won't boot
