it depends which bios you are using. the very latest x2 bios (i think this is 5035) lets you put it in f: which i recommend you put it in. try to only mess about with drive f:
in the earlier bioses (?) you can only put in c: or e:
with 5035 you can infact put it in any, c: e: or f: but i strongly sugest you put it in f: