I don't think I'd spend $100 on that. You could well pick up a much better secondhand tower for about that money.
If the board supports 133 MHz bus you should be able to run up to a Palomino core xp2100. I have my doubts about a later Thoroughbred or Barton core.
You should be able to get a S/H pally xp2000 or xp2100 for less than a tenner on fleabay.
What operating system is the machine running? How many memory slots do you have? What is the maximum capacity of PC133 memory for each slot(MB)?
There's probably people on this forum with this old stuff to give away for free... I have a few sdram modules collecting dust. Only 128MB sticks though.
Divers have pulled better machines out of a dumpster. Worth a look I reckon.
MSI K7N2 Delta2 LSR|35w XP-M2400 11x214 1.62V|2x512MB OCZ EL 2 2 2 11 2.9V|9600XT|Seasonic 350w
Abit AN7|XP-M2800 10.5x227 1.62V|2x512MB Mushkin XP4000 2 3 2 11 3.2V|9600XT|Seasonic 550w
Asus A7V600|XP-M2600 6-11x202 1.6V|2x512 Crucial PC3200 2.5 3 3 9 2.7V|PCI 32MB gfx|Corsair 450w
11:59 AM by