With LX boards, the best and seemingly final upgrade solution is to the ppga celerons, if a bios upgrade is available for the board in question. A 533 celeron on a slotket will run circles around a 266 P2 on an Asus P2L97, for example. Forget overclocking it, pretty well maxxed out anyway.
DrDemento- if that P2-400 is free, I'd give it a try. You need to be cautious of bus speeds above 75, but even that would be a noticeable, not dramatic, improvement. If your system won't run at 75, you've lost nothing but a little time.