Theres a Few you can Try, altho yes Alot Require Registration, but we all know there are ways past that... *cough*paying*cough*
EDIT:
After Posting This i came accross this one
http://www.cypherix.com/cryptainerle/index.htm
Its Free, it creates a 'container' like where u drag your Files, looks good, might try it out myself
Just Dont Forget your password, or ur screwed.
I was Using a Program called SafeSex (Created by Nullsoft, an encrypted Text Editor) was Great for Passwords, but no, i come home drunk, reckon ill change it and remember it in the morning.. i still dont know it... haha
END OF EDIT
http://www.password-protect-software.com/
http://www.folder-password-expert.com/
http://www.everstrike.com/
http://www.softheap.com/ffp.html
http://www.mycomputersafe.com/
http://www.winability.com/folderguard/ - ive used this once, its quite good for what you want to do, i used it at a course i was doing
haha locked down all my games, then just a quick click and unlocked them all, then u just have to click it again to relock, i placed it on a toolbar by the start button
http://www.pc-magic.com/dl.htm#mf - was ok, last time i used it (around win98) it had a win3.11 interface.. UGLY but it did the trick (tho, has a 30day trial which might work for the time u need it)
I think some of the first few are just same product, just rebranded.. took less than 5minutes to make that list, howww the hell cant u come up with anything?
The other thing is if u have XP Pro, just use Security Tab, but thats pointless if you are all under the same name or if someone else is an Admin so they can takeover the Folder anyway
Good Luck