Thumbs up for the WHS idea -- something I need to do as I finally bury Windows 2000 in its function to that purpose.
I'm not giving a "Thumbs down" to what's been discussed here so far -- but here's some better ideas.
Separate all the PATA drives. Go to Egg, or better -- Provantage -- and look for some good USB boxes for IDE drives. OR -- get a StarTech hot-swap bay and a spare tray for it -- for the PATA drives.
Pick the best of your SATA drives, find a duplicate of the same model and size -- lesser choice would be approx same size, different make.
Then you have two more choices: If the motherboard has onboard RAID features, you can certainly do either RAID0 or RAID1, but possibly -- with another matching drive -- RAID5.
If you have the money to spend and you want to build the server, look for a PCI_E RAID controller -- look at the Highpoint 3510, for instance. You might find cheaper, but that one's supposed to be good -- and only "second best," but gives "first place" a run for the money . . . . for less money.
Alternatively, you could get a PCI (or PCI_E) RAID controller for IDE (PATA) drives, and look for USB or hot-swap hardware for the SATAs. Or just run them as spares on your system.
And if not interested in redundancy, and IF the mobo has RAID features, you might be able to just take all, or at worst either the IDE or SATA drives, and make them "JBOD" configured.
Finally, StarTech and other manufacturers sell an IDE-to-SATA conversion plug . . . .or an SATA-to-IDE conversion plug, but I think here, especially if you're going to RAID anything, going beyond thinking about it may prove to be a headache and a deadend.