My IDEQ 200V has just R.I.P.

due to failing CPU fan... I noticed it due to system alert. It took some weeks to get a replacement & time to put it in, but very surprisingly after doing that the unit is a dead brick... I would welcome any suggestions about what else to check, as I would like to have it back to life.
The system worked great for 4.5 yrs, onaly having to put a bigger disk & RAM to keep up with demands.
IDEQ 200V KM400A-8237 mobo.
AMP Sempron 1.5 GHz
2 GB RAM
Dual boot Windows XP Pro + RHEL 4
My systems symptoms: power-on led light briefly, fans start to turn, last one or two seconds, then everything dies. PS issue ?