They are not interchangable. The only thing they have in common is the general nature of their command structure. ATA drives uses a parallel interface. SATA drives use a serial interface. They don't use the same connectors, which aren't even remotely similar.
yes, and as well as that, even if the drive from your old computer was compatible with the new one, it would still be a bad idea for various reasons, like: * most of the device drivers wouldn't work with the new hardware, so you'd have a bit of an adventure sorting all that out. * you'd be installing a disk with an old version of the operating system along with all the stuff you've accumulated on it - now really would be a good time to start again with a clean OS. * the old drive will most probably be slower and of a smaller capacity than a new one.
The list goes on - don't do it! (you can't anyway).
And to make matters worse, older versions of windows xp didn't come with a sata driver. So when you go to install windows on the drive you first need a floppy disk with your sata driver on it before you can even install windows.