I am working on a Poweredge server 1500SC running Windows NT 4.0 server SP6 with RAID 5 with PERC manager and OpenManage installed The system keeps crashing at different times: sometimes during post, sometimes while in BIOS setup, others after running fine for 10 minutes, or after running for one or two hours! (the computer suddendly turns off and immediately starts up again.) Symptoms: - the computer shuts down suddenly. Sometimes after 20 minutes, sometimes after 10. and sometimes when it tries to reboot it turns off three or four times before it can actually restart. - it shuts down during normal operation AND it also crashes when in the BIOS screen, It even crashes during POST sometimes. It even crashed when I booted from CDs and was running the Dell 32 bit diagnostis extended test. This is what I tried: - I did the Microsoft extended system test and everything passed - I checked the Perc manager and there where no errors in media or devices - I ran OpenManage and everything checked green - I downloaded the Dell 32 bit utility into floppys and booted from them. It ran 77% of the test before crashing. The only error that it picked up was: Error 4800.041F Intrusion detection bit is set. Expected no intrusion. (which was probably me opening the case) - I unplugged and reinstalled: . the processor . the RAM memory chips . the fans . the power supply and I checked all the cables, sockets and connectors. Everything seemed fine. Any ideas? My thought is that the power supply is failing or that there is a loose connection somewhere (although I can't see it!). What else could it be? System mother board? RAM memory? Your help is very welcome, Thanks,