Password Protecting a Back up Hard drive?

[Kunaak]

I have a problem I need to solve for a friend of mine.

he has a computer he shares with his little brother, and wants to be able to keep the back up drive private so only he can use it.

plus, just to be able to back up his own stuff, without them screwing it up or putting random junk on it.

I however have never needed to do this myself, so I am unsure of how to go about doing this.

any ideas?

[Hardware-Addict]

He can edit the drive access permissions ( right click on HDD icon @ My Computer & select Sharing ), and set none access to NETWORK :)

Edit ( more precisely :D ) :

He should restrict the network access permissions ( Right Click on the HDD icon -> Sharing & Security... -> Permissions... ) and set no access via user name or IP.

He can also restrict local access, by ( Right Click on the HDD icon -> Sharing & Security -> Permissions tab ) & set his bro's account with no access ( everything without tick :D )