Before you go too far, (1) the 2400 will not accept a standard ATX motherboard without mechanical (metal) modifications to the case.  (2) The Dell front panel power switch connection is both proprietary and undocumented so you will be on your own to figure out and wire in the front panel power switch to the standard ATX motherboard.  (3) You will need a new copy of Windows as the Dell provided Windows XP CD will only load on a Dell motherboard (BIOS). 

Best option, and what most do, is if you are going to buy a retail ATX motherboard, also buy a new case and power supply.  You are really looking at building a new PC, including a PCIe Video Card, new memory, etc.  I don't know if the memory in the 2400 will work in the new motherboard but it's not at the bus speed of the new motherboard so you will be slowed back down to the 2400's speed, if the memory even works. 

I know winters are tough in the midwest (I used to live across the state from you in KC), and you need something to do when there is the "white stuff" on the ground,  but really consider the new case, etc. 

One question where do type in under your name bout your info and equipment. Thanks Trafficflow

You can add your hardware profile to your signature by going to the "Community Home" page, selecting "Edit Profile", selecting "Site Options" and then adding the info to the "Signature" section.

Thanks for the location of the signature. I have checked all the specs and the mobo is a full size board that has the same foot pattern as the 2400 tower. I am not really trying to build a system. It is more like trying to get the 2400 up to a fsb of 800. If you look at the specs they are identical. Maybe the confusion is that it is a Dell Optiplex 170L. I really am looking for a chip number for a 3.4 ghz cpu that will work. Thanks for making me double check. I am starting to like the new forum also. One thing they have to fix is when you check a subscription you only get the post that apply. I had to turn hardware forum back off because I was getting slammed with notifications.

I have all the parts already and the mobo was $15.00. I have a brand new laptop and other equipment. This more of the challenge. If i would want to build one it would definitly be a quad core.

Thanks Trafficflow

You may want to look at dell outlet. There you can get a [used] computer for less than you would spend upgrading.