The motherboard is a good old Asus K7M with irongate chipset.
I'm planning to overclock it and see what it gets, after all this motherboard was famous for overclocking stability at it's time, and the Thunderbirds with it's faster L2 cache (at bus speed) and copper interconnects or something, is much more easier to overclock from tests I've read on the net.
My advice is to avoid overclocking it unless you have a very good cooling solution. Thunderbirds were pretty hot at the time and I've seen a number of them burned in the past few years.
So, what ram brand etc. would you recommend considering the bus is 200Mhz and the motherboard accepts pc100 modules (though I have a 133 128mb one in there and it works fine at 100mhz but the other one is a pc100 64mb). With the Athlon600 (older non TB version) I could raise the bus only to about 105mhz stable!!!
It's getting hard to get PC133 these days, most of the RAM brands have dropped it. Kingston should still offer it though and their products are of excellent quality so I'd recomend picking a stick from them, especially if you are going to try some OC.