stranger707, please ignore the first reply in this thread, as it is completely wrong and will cause you to waste money. Simply because the fsb of these processors are 266mhz is no indication they will work in any random board that supports 266mhz fsb. Here are the facts:
The highest CPU that can be installed on the A7M266 without extensive modifications is the XP2200, and even that is a chore. To run the XP2200 you will need an updated bios, voltage jumpers moved, fsb changed manually on the board, and a bios tweak(slew rate changed). Even then it is a toss up if it will work. It has been documented that some boards STILL won't post with this chip(XP2200), even after seasoned computer geeks have went through all the motions of attempting to install it. Even others have seen it crap out after a few months for unknown reasons. It seems to be real iffy if it will work and for how long. I know that at least a few guys have had the XP2200 running successfully on the A7M266 for quite some time now, but your mileage may vary.
The highest chip that has worked successfully on this board with limited changes that need to be made is the XP2100. If you want to save yourself a headache then buy that one, it's basically plug and go. I would however suggest updating your bios to 1008.02b. Get it from
here. If you are having trouble getting to the Asus site I can email it to you.
Also, the bios should be updated PRIOR to installing the new chip.
Hope this helps. Don't make the same mistake alot of guys did and buy ANYTHING higher than the XP2200(unless you enjoy throwing money directly out the window and wasting time). I personally suggest the 2100 as there is no real documented problems with this chip and board.
Shaidar