You can create an album on Picasa to store photos are in various folders on your hard disk. The actions you perform on the album's photos will not affect your original photos in folders. To create an album, follow these steps:
Enter the folder where the pictures and drag the right pane to the Photo Tray located in the lower left corner.
Once all the pictures in the Photo Tray, click the "Add selected items to an album in the Photo Tray and select" New Album "
In the opening window, enter a name for the album, add some description if you want and click "OK"
And presto! The album created appear in the Picasa Albums category (left column)