Belive me, your CD-ROM drive is on the list. You do not select it by drive letter, but rather by ie: Hard disk, Floppy, LAN, CD-ROM
It should be in this order.
*(PUT THOSE IN ANY ORDER YOU LIKE)
If your BIOS does not detect your CD-ROM drive do the following.
And if it is not, make sure the IDE is hooked up to it nice and snug with the red wire of the IDE in the upper right hand corner of the interface. Also make sure the jumper settings are right, it should be in "master" if it is the only drive on the IDE chain. Slave if otherwise.
Also make sure the molex (power) connector is plugged in. Also try to open the drive with the eject button to see if it even works.
INTEL i7 930
3x2gb Corsair Dominators
EVGA GTX 480