I checked out the ASUS A7M266 at their website, BIOS Version 1006 will cover up to an AMD XP 2100+ which runs at 266Mhz FSB, CPU Vcore 1.75v, you must manually set the CPU Core Voltage Block jumpers on the M/B for the 1.75v Palomino core voltage, it should presently be set for the Thunderbird core. You would also need to flash your M/Bs BIOS to the last available flash, and the last processor listed was the XP2100+, thats what I'd buy. If you live in the US or North America, you can get excellent deals and fast shipping from<A HREF="http://www.directron.com" target="_new">http://www.directron.com</A>.
<b><font color=purple>Details, Details, Its all in the Details, If you need help, Don't leave out the Details.</font color=purple></b>