MSI forum ">http://forum.msi.com.tw/index.php?board=11.0
If it's a KT133a chipset, a 133/266fsb Tbred xp2600 may go, but you wouldn't notice the difference after an xp2400. Also most of the xp2600s you see for sale are 166/333 fsb modeles which wouldn't run at full speed on that board. 133/266 barton cpus do exist but I doubt the board would support bartons. Save your money and get a new system. Old SDRAM will never give good performance, but you could try looking for some cheap memory modules and max out the memory capacity of the board if you really want to keep it.
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