Re: Computer starts up normally, a few minute later shutdown with no explanation -8200 Ellite Microt

you have to check ALL of the log files that relate to the System or the OS, not just the startup/shutdown one

google, "HP 8200 elite microtower service manual"

have you tried reinstalling windows?, or at least doing a system restore

http://home.bt.com/tech-gadgets/computing/windows-10/how-to-fix-windows-10-problems-with-system-restore-11364008291943