Allright griffia2, crash course in IDE vs SATA behaviour.
It just so happens I installed a 320gig WD SATA drive in my Dimension 4600 no less than 3 weeks ago.
What is important to note about SATA stuff is that
1- no jumpers
2- sata 0 is your equivalent to IDE 1 master
3- when put on sata 0 with an IDE as 1 master, there will be a massive conflict
that usually results in something like you have, the sata wont work, or, I've seen this before, if windows is installed on both drives, there will be a huge struggle over power between the two OS's and the system will continually reboot, never getting to either of the windows desktops.
Now (deep breath), ,, you have two choices, from what I know of the situation. Either you try putting the SATA onto SATA 1, which should make it act as a "slave" on the SATA bus, letting your master be clear and slave drive be clear, windows wont be confused. Other choice is to put your IDE on Cable select, put your SATA on 0, and install XP on the SATA (note that its alot easyer to install windows when its just the sata in there)
I dont need to remind you that if you didnt think about formatting the drive, it wont show in windows, so be sure you didnt just have that oversight