I have searched the forums a couple times and it shows that this topic has been discussed a few times before, but they were all atleast a year ago (as far as I could see.)
I ran across this program "Usb Secure"
http://download.cnet.com/USB-Secure/3000-2092_4-10966564.html
I was wondering if anyone had looked into it yet, and if it actually is a solution for this topic.
That is actually an encryption program, but many of the usb securing softwares are not opensource. Try using google to find freeware options for this. That software, and probably are all portable, but it would be a hassle to try and find one that could comply with the regulations here.
Unfortunately, password protection without encryption is kind of like building a 4 foot thick door to protect a diamond, without building any walls to go along with it.
Basically, without encryption, there are many ways (and some of them quite easy) to get at the contents of your drive.
John here has talked about implementing basic password protection into the menu, but as I said, without encryption it won't do you all that much good if you are really worried about the sensitivity and protection of your data.