Question : Problem: Catastrophic failure. RAM tested as failed -- replacing RAM didn't revive system

I have a desktop unit based upon the Asus P4P800S-X motherboard (Intel 848P chipset) and a 2.3 GHz Pentium 4 processor (Northwood). Two 512MB Ballistix DDR DIMMs. Running Vista Business. Had a catastrophic failure two days ago while in the midst of trying to install SP1. System powers up, goes through the POST, fails the minute it starts loading the operating system, complains about a corrupted NTOSKRNL.EXE. I suspected a hardware failure.

Mem86 test (booting to the Mem86 CD) would not complete even a single round of testing -- would freeze at the start of the third test with no error message. When testing each DIMM and each slot separately, got the same result (freezing at start of the third test), except I get a single error message on one of the two DIMMs before Mem86 freezes up.

Installed two brand new 1GB DDR PC3200 modules -- got exactly the same symptoms. Mem86 still freezes at the start of the third test.

Replacement motherboard already ordered -- will use it as a back-up if the problem proves to be elsewhere.

Any thoughts or suggestions would be greatly appreciated.

Answer : Problem: Catastrophic failure. RAM tested as failed -- replacing RAM didn't revive system

This makes sense as the memory testing works OK if the USB devices are disconnected.  The USB problems indicate motherboard failure of some type.

The DVD problem doesn't.  You'd need to test the DVD player on another system to see if it or the motherboard is the problem.  Plug it into another system and see if the Vista DVD will boot.  Just boot; nothing else.