|Ways to test include viewing event logs. See also if any dump logs exist.|
Use performance monitor to remote log on networked system. It may help in looking for clues.
Consider tools like ultimate boot cd. Use memtest and hard drive diags.
See also power supply and temperature issues.
Possible that even ups is going or input power has issues. If one has many power supplies on a circuit it can create harmonics. It can trip breakers and burn connectors. You'd need a professional electrician with special fluke meter to diag that.
Why did it take me over a year to phone in a problem to ATT?