It sounds like your board is a 200Mhz DDR(100Mhz real) FSB board only.
You can install a 1400/266 Athlon in it, but I think the most you will be able to boot it at will be 1050Mhz by default.
If your chip is unlkocked, and your mobo allows you to, you (using latest bios) should be able to configure a multiplier of 14x or more. This will allow you to try and set the chip for 14x at 100FSB giving you a 1.4Ghz cpu again.
In reality you can probably overclock your FSB a little, but on that chipset it is a crap-shoot and could be 1-10mhz extra, giving you a theoretical limit of 1155Mhz or so, without adjusting multiplier.
Basically, you can use the cpu, but it will be severely throttled on that board. If your memory is good, you could upgrade to a KT133A board (such as A7V133) however if I were doing it, I would take the hit and drop SDRAM support totally and go fully DDR, either with a Sis735 board (see THG review of such) or with a KT266A (note - get the A revision) board such as the K7T266 Pro2 (the 2 has the KT266A) from MSI...
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