|The failing power supply may have damaged the motherboard but usually if it posts OK then the motherboard is OK, (usually).|
But are you sure you reconnected everything right? Most of the time the cables will only fit one way but if you're unsure, the red-striped edge of the ribbon cable connects to the # 1 pin side on both the drive and motherboard connector.
And, did you remember to attach the power connectors to the drives?
Also, go into cmos/bios setup and make sure the floppy and IDE controllers are enabled and the drives are properly identifed--1.44 for the floppy and probably AUTO for the hard drive(s). Check that the drives are in the boot order
Real men don't use AntiVirus; they just reformat