|Every thing is fine until cdrom is used...hmm|
if you had two cdroms I am sure you would of tried both..
Best answer so far....your power supply can't deal with the extra load or the cdrom is going bad.
cdroms are inexpensive and easy to replace.....even a garage sale cdrom for testing can save you some money.
Power supply's are also very easy to replace. If you do not have a tester take the power supply out and have it tested at a shop.....A moms and Pops shop will most likely do it at no charge. 4 screws and a few connections to unplug.
Depending on the age of the system new or used parts might be a factor...