I teach at a local college, and one of the courses I teach is the Intro to Computers course. We cover a lot of material, including the Microsoft Office tools.
If there's one thing that I want students to remember about Microsoft Office, it's this: Don't forget your password!
Here's the scenario. You have an Excel spreadsheet that contains confidential information, so you protect it with a password. This is a feature built into Excel. When you do a File->Save As, go to the Tools->General Options menu (the Tools menu on the Save As dialog, not the main one). You can enter a password. Thereafter, if someone wants to open the file, they need the password.
This is great from a confidentiality perspective. The problem is, people are always forgetting their passwords. This is apparently a big enough business that programs are sold for the sole purpose of recovering these passwords. And it's not only Excel and Word, but zip files, Quicken files, etc etc. If you can password protect it, you'll eventually lose the password.
Password Recovery Solutions is where I usually send people who've forgotten a password. The chance are good they'll have a product that'll recover the password for you. You'll pay for the product of course, but that's the cost of forgetting the password in the first place.
My advice? Don't use passwords on files unless it's absolutely positively necessary.