Best method to password protect usb drive / external HD?

[MGB_]

I've been using TrueCrypt on drives with sensitive information, and it works great, but whats the best way to protect usb drives that doesn't require software installed on the host computer?

I don't need encryption or super great security, nothing is really to important. I'm just looking for a method to password protect either the whole usb device or a folder within. Again don't need strong security, just if I'm passing my usb around at work to hand out files i can prevent them from opening/copying certain files.

Thanks!

[MGB_]

Also- I should mention this will be used on Windows 7 and XP platforms.

[SpiffyGTI]

With no software required? Stick files you don't want people touching in a password protected .zip file.

[bora.the.explora]

i use this software free method for my stash of "stuff". it's secure enough for me.

[Hostile]

TrueCrypt doesn't require software to be installed on the computer.

There is a version that is self-executing that you can copy on the drive, outside of the encrypted partition.

EDIT - When you install it on your end you are prompted to either do a full install, or create a portable installation. This portable installation can be put on the drive.

[Angry_Birds]

If every machine is Windows look into BitLocker.