there is this real nice software called HIDE FILES AND FOLDERS
its a free 30 day trial...u can get around that by looking for serials on google BUT ITS ILLEGAL SO DONT DO IT...
if u want i can mail it to you though u should be able to find it on google easily
though the name says HIDE, it has the function of password protecting also
and u can set the time limit that it stays unlocked once u've ritten the password
so for example u want to give sum1 access to the fodler just for an hour, u can do that also...