sorry about the slow reply jeremy. have been offline for the past few days. thanks for providing the hardware specs for your system. the HP ProLiant ML350 G4p Storage Server is a nice chunk of metal... you could do a lot with Xeon processors
since you have hardware raid, you will probably want to use it, as it's _usually_ the easiest way to get things up and running. but there are some hurdles you will need to overcome. 1st, determine what chipset your hardware raid is. unfortunately, the information from the link you provided isn't detailed enough. once you have determined the chipset, it will reveal whether you have "real" hardware raid or "fakeraid". either way, you will need to check whether your installed version of FC4 supports your raid chipset.
as i'm not familiar with fedora's hardware compatibility, it might be worth checking out their website. otherwise, there should be someone here to clarify this.
once you've determined it's compatible, you should make a full sector-by-sector backup (similar to ghost or SystemImager backup) of your main hard drive. then, you can enter the hardware raid's bios (check your hp user manual or cd, it should have details on how to enter this - u might have to press F2 or some other key combination right after power on), and make a "mirror" copy of the primary hdd. make sure you DO NOT mirror the secondary hdd to primary, otherwise both hdd's will be blank (assuming secondary disk was blank). hence, ensure you have made a full backup of your primary hdd 1st.
once this has completed, you should exit the raid bios, and the computer should automatically reboot. assuming it was successful, you will be launched back into linux. that's it!
if you want to test whether it was successful, turn off the machine (and unplug power cord; otherwise the 5VSB will still be on), and unplug the data & power cable for the primary hdd. then plug the power cord back, and turn on the computer. if it worked, you should be back right into linux.
please note that you _may_ experience problems booting due to bootloader problems (eg. grub/lilo). this does not mean that the raid mirror copy failed - simply the bootloader was not setup for booting from the secondary hdd. as im not familiar with FC4, you will need to check with someone else to confirm this.
hope this helps! let us know how you go...