I have a second PC running XP SP3. It's a 2007 Dell. SATA drive connectors, upgraded to the full 3GB of RAM that XP can use. I use it mainly for games that 7 can't handle well, since I seem better able to run DOS games on it(even with DOSbox, my 7 PC doesn't seem to like them as well), it can handle the 16-bit programs that 64-bit 7 can't run, and some other games have given me issues in 7. Firefox runs on it.
I'd wager though that if it's an early model PC from 2001-2004 it's probably no longer a useful machine, hardware or software.