PC was working. The other day would not boot, no post, but after checking cables etc it started OK. Tonight no post, no power light on case, no HDD light. Fans run, power light pn mobo on, system checks CD, but nothing else.
Went back to bare board, graphics keyboard & one stick of memory, ps2 keyboard and mouse. No change. Other stick of memory. No change. Tried memory from other PC - no change. Checked graphics board in other PC - no problem. Checked monitor - no problem.
Forgot to mention - successive power failures severwal nights ago, but power goes through a surge protector that is still green - and worked several times since anyway.
Tried CMOS clear, tried most things I can think of. Hmm - power supply mobo or cpu. I'd choose power supply but open to advice.
Further info - USB laser mouse does not light up. PS2 keyboard single 'on' light. Pressing reset does not seem to reset (inasmuch as when sata cd plugged in it does not retest). System is watercooled and I notice that even with radiator fan off water lines coming from CPU are not even warm.