Adding hard drive on a p4c800e

I currently have 2 raptors on a raid 0 using the intel raid controller.My question is I want to add a additional 80gb sata drive for storage how would I go about that.....

You need to enable the promise sata controller and just go from there. Make sure you have updated drivers for the Promise, check Asus's website.

Or you can just plug it into an IDE connector and turn the computer on. I'd split my Cd drives and put it as a slave on one of those IDE channels. You will only need to use the promise controller if you want it to be a part of a RAID set up. Windows will see the new drive and assign the next letter to it. I've got one on my rig configured this way.