I have a Dell Optiplex GX280 that's restarting randomly. I've checked everything I can think to check, and still can't find the cause. The user describes the restart (which, unfortunately, I have yet to be present for) as: "A quick, high whine, and then it turns off." I've tested the mobo, proc, memory, HDD, and power supply. I've checked the fans. I've checked for blown caps. I've reseated all connections. I've even replaced the CMOS battery and PSU with known good/working ones.

I don't think it's going to be anything related to software, since the user has indicated it doesn't seem to shut down on her while she's doing any particular thing. The high-pitched whine she describes should also be a good indicator that I'm looking at a hardware problem, I should think.

My first thought was PSU or possibly fan failure/overheating, but neither appear to be the case. Any ideas?

Any advice at this point will be greatly appreciated.

- Devin

Have you checked and/or reset the bios? Just a gander, it may be LAN.

The BIOS was reset when I removed/replaced the CMOS battery, and I made sure to check all settings while resetting the clock. Everything's in good shape, as far as the BIOS is concerned.

Thanks for the reply, and if you have any other ideas, please let me know. I'm still completely stumped.

- Devin

first got to control panel - administration tools - event logs does it give any error codes that could point to a problem.
also if you right click on my computer, select properties - advanced -startup and recovery. if you untick automatically restart the next time it fails you will get a blue screen with error codes these can be checked on the microsoft website for further pointers. once you have got these restsrt your system and set it back to automatic restart.
you may find its as simple as a dodgy driver. if unsure post the err codes and i'll see what i can find out

Thanks for the advice. I'll give both of those a try and see what I come up with. I'll post the results as soon as I have them.

- Devin

Okay. So I checked the error log (there are plenty, but nothing to cause this that I saw), and then went into system properties to uncheck "Automatically Restart" if it needed it. It didn't. As I was sitting pondering how this could be the case when I was not seeing any BSODs after a crash, I was fortunate enough to actually witness the "crash" for myself.

The high-pitched whine the user described to me was actually a single beep. A single beep produced by the UPS as it temporarily lost all power and then came back up. I replaced the UPS, and we've had no more problems.

Thanks for the help and suggestions. In spite of the outcome, I still really appreciate the assistance.

- Devin

Don't you just love end-users?
Good to hear you tracked it down.