I assume the POST is hanging at "Detecting IDE drives"?
It could be a bad drive or IDE cable, or cable not fully plugged in, drive jumpers not set properly, or corrupt CMOS.
First try resetting the CMOS by moving the reset jumper (with power off). It is on the motherboard close to the battery.
If that isn't it, try unplugging all drives to see if POST progresses past detecting drives (it should show "none" and continue until it says you have no drives). Reconnect your drives one at a time. If the problem comes back, see above.