Thanks for the feedback guys!
you could just get a 600mhz celeron (they are 66fsb).. they use less V than the PIII (ie cooler), and i'd think a 600mhz cel (pIII based) should outperform 450mhz PIII, even with less cache and fsb.. and be cheaper on ebay.
I think it will use slightly more power because it's pretty much the same core (Coppermine vs. Coppermine128) clocked 1/3 faster. Also I thought Slot 1 Celerons were only available with the older Mendocino .25 Micron core, although I guess if I need I could get a slot-to-socket adapter as well.
I have done a mod with a broken XBox and an old flex ATX MB that has the FSB at 100Mhz. I have several (5) PIII EBs (133Mhz) that are working happy at ther rated FSB, but refused to work on my 100 Mhz board. The only ones that work there are the PIII 800 EB, not the 667, nor the 733. So if you want to be sure, is better that you buy an 100Mhz Celeron.
Interesting.. any idea what the board was or what chipset it used? It seems really odd that it works with the faster chip, I'd expect it to be the other way around.
I don't really want to have to muck about with a socket adapter, but I guess I can if need be. I'm still tempted to try the PIII and see what happens, but I think I'll start looking out for Celerons on eBay being sold with adapters too. I'll let you know what happens. Thanks again!