I'd have to agree with avdven, the power supply may be a big part of this. If your power supply is hovering around the 100 watt s/output level, you need to consider another power supply. I tried connecting a CD-RW to my (t)rusty little Compaq, and it wouldn't boot up with both devices attached. Any power-drain is going to suck resources away from something else, and a hard-drive ( or CD_ROM for that matter) can be the worst of the culprits. If your memory isn't getting enough juice, you'll get errors, or simply no-boot/POST error codes.

zaddikim