I should mention here that I discovered and cleaned out some serious dust bunnies from the CPU fan some six months ago, which may have fried the CPU. But like I said, it was working fine until this week.
I've gone through the troubleshooting guide for boot/video problems:
- I've connected the system speaker to check for beeps, but there are none.
- I've also tried removed everything but the CPU, the CPU fan and case fan, but there are still no beeps.
As far as I've understood this translates to dead motherboard. However, I don't have a voltmeter - could it be that the PSU is at fault?