bcos the drive where my OS is is 80GB and my user folder is around 100GB by itself
anyway
i worked round the problem
i set that reg value to the new destination, made a new user, then copied the files into the new User file. then, a stroke of genius if there ever was one, i copied the Appdata hidden file to the new user which copied all my firefox extensions etc.
brilliant!
i am happy now
thanks for ur help guys, as always