Windows 7: Password Hard Drive

Hello everyone I have a few problems today. My nephew some how found his way to my 120GB back up drive (receipts/records/taxes/etc) while watching his choo-choo train song (he is 6). So this has me worried and I am curious is there a way to make a storage drive require a password to access?
I don't want to setup user accounts or anything like that, I just wish to have to login each time I click on that storage drive, however if possible I would also like to restrict searches on that drive too if possible.

Anything out there that could help me?

Google

how to password protect hard drive? - CNET PC hardware Forums

My question is by using that if I was to transfer all the files to a flash drive would they be readable on other computers? I am just in need of light security and by those threads it sounds like it might permanently alter the files.

Nope that is a different problem with a different solution.

If you password protect a flash drive it may not be readable on other computers. Have you googled the problem?

Of course but it leads me to programs like bitlocker or truecrypt which is high level security. All I am trying to do is a simple password so I can keep kids out of the drive. While I make monthly back ups via DVD I like to have digital copies of all transactions of the past 20+ years.

With most solutions though it seems to alter the files making it unusable on other systems or is so tedious that I would turn it on and off 10-12 times a day to keep the info safe. I work at home so I am up and about a lot.