+ If you really want to find out what your board supports, I would check MSI's site out for updated bios' and then read the changes to the updates. You can find out what the board may support now and it should give you a better understanding of your upgrade path.
If your board supports a Tbred processor, then you can probably upgrade to at least 2Ghz (the 2400+), but I would check to see just to be safe. Good luck, and welcome to Anandtech forums!
Edit: I just checked out a site and it says this
6561v16.zip bios has this:
"Release: 2002-10-03
-Support AMD Athlon XP 2400+ & Athlon XP 2600+ CPU
-Fixed system cannot used Broadcom LAN card "
This leads me to think that the mobo will support a pretty fast cpu (ie. the 2600+ is 2.133Ghz which is one of the fastest cpus out now from AMD).