Password-protecting Word documents

Not many people realise you can lock Microsoft Office documents (Word, Excel, etc) so they can only be opened with a password. Great to protect family recipes or whatever from prying eyes. The method is much the same in both Word 2003 and Word 2007, except the buttons are located in different places. Here's the procedure:
1) Choose "save as" from the File menu.
2) Click on the "Tools" button, which I bet you have never noticed before. It's top right in the 2003 version of Word, and bottom left in the 2007 version.
3) Choose "General" options, and a dialogue box will pop up in which you enter your password. You can also have a second password for modifications, so people can access to read but not to modify the document.
Warning: Don't forget that password, because the encription is so strong even computer experts probably won't crack it.