can't write on hdd????

hey, i'm not exactly a noob with my xbox, but i am with hdd's. i'm trying to change my dash, and i know how to do it , but inorder to i have to write on my cdrive in my xbox, unnforntunatly i can't put anything on nor take anything off anymore.

ps i am currently running unleashx if that helps any.
pss i am installing xbmc, if that helps.
thanks in advance,
jkl