I'm putting an old parts back together again. They were in working condition. I have a msi KM4M Mobo. AMD Athlon A1333AMS3C CPU 20GB HDD 256 Ram 1 used 300w PU and one old CD-Rom They all were working last time I checked. I connected the HDD separately to IDE1 and the CDrom to IDE2. Both being masters since they are having their own IDE. I start the PC and there is a sqealing noise. I messed around with it alot and I found out that if only one of the Drives are connected to the PU the sqealing stops. If I pull the PU from one of the drives, it turns off. Bottom line is that when both are connected to the PU, the CDROM is not working. No light, no ejection button working. I haven't hooked it up to the monitor yet and see what it looks like, but if the CD ROM is not working then I would assume the HDD is not receiving power either.
To start, get a new PS, 450W or better. Sounds like you are overloading the power supply or the power supply is defective. Could be that capacitors are blown on the Mobo, but I'd bet PS first.
Check on the side of your power supply to see if it has multiple 12v rails. If it does, you can try connecting the two drives to different rails in order to ballance out the power load. If that does not work, you will have to buy a better powersupply (it won't cost much to get a unit that is better than what you have).