hmmm – good question.

As you apparently know, the People groupings in Picasa are just like Albums (actually, they *are* albums … they're people albums) therefore, deleting a picture from the person's album, does not delete the picture from your computer.  The People albums are just a way to group pictures together.

To delete one of the pictures, you would need to first right click on a picture and choose, “Locate in Picasa” … now you're looking at the actual picture in its folder and deleting it there will erase it from you computer.

OK, so … our goal is to get a group of pictures in their folders that is the same as the group of pictures in the People album.

Here's how I would do it …

View the People album, let's say there are 85 pictures showing of Harry.  You can select all of them and then add a tag (see the Picasa video #22 on tags) 

Make sure the tag is something unique, like DeleteHarry … you don't want to add a tag just 'Harry' because when we search for this tag later you don't want to get pictures of some other Harry included in the mix.

Ok, now that you have them all tagged with 'DeleteHarry' you can search for DeleteHarry – you should now be seeing search results of the 85 pictures that you tagged.  Select the Search results (in the upper left) (this is demonstrated in video #51 in the Picasa Series) Check that all 85 pictures are in the selection tray.  Now you can press the Delete key on your keyboard, it should as Are you sure you want to delete 85 pictures?  If that's right, go ahead and click 'Delete Items'.