Hi, I've looked around and it seems no one has a similar problem.
My computer is currently running on a PATA harddrive. It is on XP with SP3.
I added a second harddrive (SATA, Seagate 120GB) and it also has XP with SP3, but the OS has a few problems, so I was going to use it as a storage HDD. But when I boot into windows on the first harddrive, it doesn't show up in my computer, anywhere on disk management, nor in device manager. However if I change the boot order to use the second hard drive first, everything works fine. My motherboard is an ASUS A8V Deluxe Motherboard, so my second hard drive does not require a jumper. How do I get my second hDD to show up?
You could try Setting the Jumper on your PATA Drive to slave the change boot order to boot from your Pata Drive, see if it shows up then.
I actually had this problem once, but it got fixed by making my boot IDE drive into a slave.
Also, you could Move all the files to your New Sata disk using http://clonezilla.org/
and start using the sata drive as your primary boot drive, then used the IDE drive as a Extra disk for Games or pictures or other things.