From Vista help;
Open the folder that contains the file you want to change.
Right-click the file, and then click Properties.
In the Properties dialog box, click the Details tab, click the properties box that you want to change, type a word or phrase, and then click Apply. (If you don’t see any text for the property you want to add, point to the place where you would expect to see text, and a box will appear.)
To add more than one property of the same type, separate each property with a semicolon. To rate a file by using the ratings property, click the star that represents the rating you want to apply.