Ultra ATA is nothing like SATA. Your Ultra ATA hard drive is running off of an IDE ribbon. SATA uses a completely different smaller, and faster cable. Also uses a smaller power connector than your generic 4pin molex connector. If your hard drive is ATA133 which I would assume it is, then that's 133mb/sec transfer whereas SATA is 150mb/sec I believe. Not only that but you can get of course the 10,000 RPM SATA drives which load games, windows, copies files and all that HD kind of stuff very quickly.
It supports either, thats why it is working.
Next time it'd be helpful if you could point him in the direction of a resource to answer his question. Being that the two are completely different this really leaves him in the dark.