Your 5V is way below spec. For 5V min voltage for TTL lodgic is 4.75 V.
As jamesgoddard said your +12 V is ay low also. And Your system is at idle, Under load they will drop more. Hopefully the software is not providing a correct reading - Doubt computer would boot with 5 V at 3.7 volts. As chookman said, check in bios. Might also try different software.
Also check voltages under loaded conditions (ie run a 3D app like ati tools - view 3d, or that furball benchmark program.
Even better get a cheap DVM and measure the red and yellow -> black at one of the molex connectors