I have a server which was running for years without any issues and suddenly the other day starting freezing with a black screen. Running SBS 2003. It happens at strange times, so far never at the same time, and not in any sort of pattern I can really define, except always in the middle of the night between 9:30 PM and 6 AM. I've disabled backup jobs, Shadow Protect on the C:\ drive, VSS and WSUS, as well as all jobs in the task scheduler. Still it locks up. I saw someone suggested heavily fragmented c:\ drives could cause that, I checked and used Diskeeper to defrag my c: drive, took multiple passes all day with it until all the red fragmentation turned blue. I even freed up some space on the c:\ drive so it went from having 15% free to 30%. The black screen persists. The symptoms are like this - the server's running along great, until suddenly the screen on the monitor just turns black. No mouse, no icons. Num lock on the keyboard does not work. CD-ROM drive ejects ok. Server quits responding to PING and loses inbound and outbound network access. No blue screen, no error message. A reboot by holding down the power button on the front brings the server back up fine for a few hours, and then bam it goes down at random again. Checked the event logs, hoping to find a smoking gun like a common event id right before the lockup, but the event logs don't show any errors or warnings around the times of the lockups, and the last event logged is the winhttpautoproxy service logging it's standard information which shows up in my event logs all the time. I looked for memory.dmp but it was empty also. Any advice?