I remember my old XP 1800+ (Thoroughbred). Clocked to 2.2GHz. That was so fricking awesome.
If I remember correctly, XP 2100+ where either Palominos or Thoroughbreds, the latter being a decent overclocker (my XP from above).
@ OP: Since the chip has a 266 FSB, you could try upping it to 400MHz (if the mobo can handle it). Use a divider for the RAM, unless you got some PC3200, in which case you could run 1:1. Those chips rarely went over 2.4GHz, so don't go crazy with it (2.2-2.3GHz should still be withing reach thought). And remember to not go over +0.3V on the vcore.
Edit: Stock cooling won't allow for much. I wouldn't go any higher than +0.1V with it.