It is possible to interchange the floppy disk drive with the CD-ROM drive. Whether you are replacing the CD-ROM drive with the FDD, or the FDD with the CD-ROM drive the procedure is similar;

1	Remove any disks from the drive.
2	Shut down the computer, and turn it off.
3	Turn the computer upside down, with the front facing you.
4	Slide the drive securing button to the left while gently pulling the drive outwards. The drive should disengage from its connections. Slide the drive out of its compartment.
5	Put the removed drive in a safe place.
6	Insert the other drive into the vacant compartment, ensuring it is the correct way up. The drives only fit one way, so if the drive only moves so far, you are inserting it the wrong way round. Push the drive all the way back until it clicks into place.