TOPIC: Password Protection

Hello everyone
I want to password protect my external hard disk. Surfed through web and found we need to use a 3rd party software to have a password for the hard disk. Can I use the external hard disk on some other system which does not have the 3rd party software installed in it?
Did anyone use this method? Please help!

1) What OS u and the other system are on
2) if Goal of password protection is securing data...that can also be done by other means

You would be looking for something like the below.

www.magic2003.net/

Fully portable use, you may take it to anywhere on the fly without the software installed on each machine.

I highly recommend
www.truecrypt.org/
since (1) I have been using it since 3 years (after made my own capable (which itself is questionable, though) Googling with no single complaint or hitch (well, read FAQ, creating a truecrypt file is 'bit' tricky and also it is recommended to leave 1GB / 2GB in the HDD 'open') (2) Several versions are available (PC, MAC, Linux) including PORTABLE mode (highly recommended for day-to-day use and also for 'no' need to install on others' systems.
Give a try and in any case (sticking to it or . . .) give your inputs too susbequently
Sincerely

Further, just forgot, it is freeware as well.