Somewhere in the Bios, all the drives will be listed (i.e name, size, parameters, translation - such as LBA etc). Look for the CDROM drive & let us know what the settings are for it.
However, starting to think that may not be the problem.
Can you tell me, when you reformatted, did you repartition the drive at all? If so, how many partitions did you have before & how many now?
Also, what OS are you using?
Another thing to try :
create a boot disk that loads CDROM driver in DOS (e.g win98 boot disk is ideal). Boot the system from this, let it load the mscdex driver for the CDROM, then insert a CD & try to read it in DOS.
(Use the dir d: command assuming that DOS assigns drive letter D to the CD)