|IDE hard drives are available:|
Sata PCI cards:
but as mentioned above, look to see if you actually have SATA connector, many MB's had them before they were common or inexpensive so the machine may have been built around what was cheaper rather than what was best at the time.
If the machine is really old, avoid spending too much on it as you will probably want newer/better soon anyway.
You have to be a little bit crazy to keep you from going insane.