The Athlon XP 2600 comes in either a 266 or 333 version. If it's the 266FSB version, your total clock speed as reported by Windows will be 2.13GHz. The actual figures are 133x16. (not sure about the 333 version)
Here's the biggest thing of all. If you've run this processor for any amount of time at higher than 60°, you risk damaging the processor. The fact that you've been running at almost that is more than likely due to the fact that the computer builder used the heatsink that shipped with the processor, which is woefully inadequate for everyday usage. Go to
Cooler Guys or
Hardcore Cooling and get an AMD XP specific heatsink/fan combo. Also make sure that airflow within your PC is not restricted, and that the air coming off the proc fan is directed out of the PC as quickly as possible.
I burned out my first 2100+ because I didn't read up on this kind of stuff. Unfortunately what expertise I now have cost me around 300 bucks.