Lo dudes! Right - what u need to do is:

a: copy the files tfc.wad and tfc2.wad from the tfc folder into your valve folder
b: if the he_lowgrav.bsp isn't already in your cstrike/maps directory, make sure it is!
c: extract the moon.wad file to: valve/ cstrike/ and both the map directories (it only needs to go in one, but i can't be arsed to work out which).
d: ermmm... i think that's it