Make sure that the IDE channel that the drive is connected to is enabled in BIOS and the channel has no problems in Device Manager, make sure that its cables are securely connected, check that the red or blue or gray stripe along the one edge of the IDE cable is next to the power cord on the back of the drive and next to pin 1 at the MB connector, try different jumper settings and a different IDE channel, install a different known working IDE cable, and connect a different power lead to it.
If no luck, then start up with a Windows 98 boot floppy inserted, select 'Start with CD-ROM support', press Enter, at the A:\> prompt type DIR X: (where X is your CD-ROM drive's assigned letter that's noted just above the A:\> prompt), insert a data CD, and press Enter.
If you do not see the contents of the CD, then the drive is probably bad.
Or see if it works in a different system. If not, then it's probably bad.
If not, then it's probably bad.