If you work on a shared computer, you might want to password-protect your excel or word documents. How would you do it?  There are a number of commercial tools available for this, but Microsoft provides a free, nice and elegant way.
The first time that I needed this feature, it took me a lot of time researching, so thought of sharing this tip with you all.

If you are using MS Office 2000:

1. Open the document.
2. Go to File > Save As. Click on Tools on top right side as shown.
   
3. Click on General Options.
4. The next screen will ask you for the password. Fill in your desired password.
5. The next time onwards, whenever you open that file, the system will prompt for password.

If you are using higher versions of MS office:

Microsoft has made this process a bit simpler for higher versions. Simply go to Tools > Options > Security tab and fill in the desired password.