What Javo said is technically true, but everything will go smoother if you do a more direct replacement. Less to worry about. Plus, you'll never actually regret having ATA, because you won't be able to tell the difference.
Open up the case. If there are SATA ports on the board, then there is absolutely ZERO problem with getting a SATA drive. The other thing to check for is a SATA power connector available. If you don't have one, don't worry, drives typically come with one. (They use a different plug.) If you buy an OEM drive (no box, just drive.), then you'll need to grab a power connector for around $3 (assuming your PSU doesn't have a connection for it.).
If your board doesn't have SATA ports, you can get an add-in card for probably about $20, but that's more trouble than it's worth, just get an IDE/ATA drive.