Hook up your hard drive to the Promise ATA card if you want to use the high speed transfer. Leave the CD-RW drive as Secondary Master on the IDE controller on your motherboard. The fastest a CD-RW drive will support is ATA33, so its basically useless to hook up a CD-RW drive to the Promise ATA card. Even with the ATA33 (33 MB/s), the transfer speed between the computer and the CD-RW drive will never reach that speed. If motherboard on your system already supports ATA100, I would just return the Promise card, as its useless to you unless you need the extra IDE controllers.
And if you wondering why there are no ATA66 or ATA100 CD-RW drives, just read the following thread.