Ryan, why not just buy yourself an external FireWire/USB equipped external enclosure?? Then you don't need to install any PCI card. It makes the most sense these days.

Making sense of it all
Ms. Remy Ann David

Ryan

If this is an ATA (PATA) not a SATA drive. I assuming both SATA
bays are full???

Ive been using 2 SATA drives, and a PATA drive on my dual G5 for 9 months now with no issues, in fact I made the PATA drive the boot drive, and use the SATA drives for audio and video respectivelly.

Going strong 10 hours a day with Protools HD.
I had no PCI slots left!!!!!!

See below:

Get yourself a Y power cable, and a dual ide cable ($5 at Rat Shack), replace the
optical drive's ide cable with the dual, plug the Y cable to the optical power cable.
The new Y cable will power both the optical and ata drives.

The get some 4" wide velcro with the adhesive backs.

Remove the optical drive, velcro the new drive to the ceiling of the G5
case above the optical drive.
The optical ATA bus will accept a hard drive!!!
Make the optical drive slave, make the hard drive master.

The newly mounted drive will be in the upper quadrant airflow, there is no cooling issues.

Peace