nsCOMPtr<nsIPref> pPref(do_GetService(kPrefCID, &rv));
nsCOMPtr<nsIPref> pPref(do_GetService(NS_PREF_CONTRACTID, &rv));
void DIR_ClearPrefBranch(const char *branch){	nsresult rv = NS_OK;	nsCOMPtr<nsIPref> pPref(do_GetService(kPrefCID, &rv)); 	if (NS_FAILED(rv) || !pPref) 		return;	pPref->DeleteBranch (branch);}