Lets see
133 is the bus speed of the "motherboard"
the INTERNAL speed of the cpu is 2x133 so you are right it is 266...that is the INTERNAL cpu speed. (or for the newer Athlons it is 2x166 or 2x200)
You're memory happens to be DDR so its is also 266mhz (133x2)
I notice you have a stick of PC1600..now that is designed to run at 100mhzx2. So either that stick is overclocked to 133 OR the OTHER stick is underclocked to 100mhzx2....so if I were you I would check that out in the bios and see what speed the memory is running at. If it is only running at 100mhz then you are losing a lot of performance right there...so you need to try to run them both at 133...and if the pc1600 wont run that fast then youd be much better off to get rid of that stick and get some more PC2100....you will have much better performance that way.
(here is a little blurb about memory speeds and naming etc
http://www.purdue.anderson.edu/Cpt/C...dr%20sdram.htm )
I dont think there is any difference in performance between having one stick as opposed to two.
Here is the page with all the specs, drivers, etc etc
http://tw.giga-byte.com/MotherBoard/...ts_GA-7DXR.htm
Evidently it goes up to an AthlonXP 2600+(.13u) with a 266mhz....if you go to upgrade just be careful not to get the XP2600 that uses the 333mhz fsb cuz your board wont run that one.
You probably need to get the latest bios to run an XP2600.
Revision "BO" is the "stepping"....I dont know why they call it that though, lol.....it is like a "version" determined by what "batch" the processor came from.....different batches and "steppings" have some slightly different characteristics since they learn better and the process improves along the way etc....so certain "steppings" are known for instance to be great overclockers and some are just average etc. The overclocking sites have lists of which ones are which etc.
JP