I'm in the same boat as you. I have an Asus P2L97 (LX) and am leery about buying a Celeron CU and not having it work. I've already talked to a couple of local stores and they won't let me bring in my system to test. Worse yet, they advised me the warranty to nil if I try this, whether it works or not.
This is what I've been able to dig up so far on this subject:
The motherboard needs to have an on board regulator that will support the core voltage of the cpu. A celeron ppga requires 2.2, 2.2, 2.0? Somewhere in that range, but I'm too lazy to check. The celeron cu's require 1.6, 1.65, 1.7 for the range of them, with the higher ones requiring the higher voltage. Most people go to 1.8 for overclocking to 800+. Most LX chipset boards will support *down* to 1.8V. This means you're in the right ballpark to drive the cpu's core voltage. Check with Soyo to be sure! The asus I have will support 1.8v.
A good slotket that allows voltage adjustments on the card is a must. The CPU will autodetect it's required core voltage, but if the motherboard can't supply this, the thing won't run, or will will get a possibly wrong voltage. (50V!?!) This is more of a being careful thing, but could save the cpu from being well done.
A good quality hs/fan combo is a must as you will probably run a higher than spec voltage for the cpu. This means extra heat and lower heating bills! I would suggest a gorb or chorb because they're light and effcient. Stay away from a copper unit. They're excellent for cooling but weigh a ton and I'm not comfortable suggesting putting this kind of strain on a slotkey and support posts for a slot 1 motherboard. Don't forget premium thermal transfer compound!
Upgrade the bios for the final step! If the cpu won't work with the bios you have, try different revisions. What is needed is the microcode for the cpu. If it's not there, the cpu probably won't run.
I think that's everything that should be on the required list if you're gonna try this. I think I may give it a shot soon. I just need to find someone who buys a celeron cu system and will let me demo the cpu they have!
PS - What kind of config are you running now? I used to be a p2-233, upgraded to a p2-266, overclocked to 333. Now I managed to get a celeron ppga 533 running with an asus slotkey!!!. (voltage settings on card) This is pretty good, as asus told me I would never get anything over a celeron 466 running with this board. It just took bios 1010 beta 3 to do it! The cpu runs at the default voltage required, and is stable at both 605mhz (75fsb) and 670mhz (83fsb). That's where I'm at now. This is fast compared to the old 233 system!
Best of luck at trying this.
I think tom's hardware should consider an article about running the celeron on an lx chipset. I enjoyed the one about upgrading a socket 7 with an amd k6-2 thoroughly! I even had the pleasure of upgrading a system with the asus p55t2p4 they did the special article on. Was that a joy!
To Tom, or anyone in your organization, if you read this, feel free to contact me. I would love to see an article on this subject!
and the voltage is autodetected... The question is, how would the mobo behave if a Cel II is put in it?? 
Facebook
Twitter
Instagram