Running Vista, have External HD for Backups

Have used this backup drive for a couple of years; no problems with it.

Purchased new laptop running Vista 09/01/07. In Control Panel/Backups, etc.,
set it to run backup of My Pictures and Documents every day. No problem. Have
referred to the Ext. HD on several occasions to find a pickture, etc.

Came home three days ago to find a message on my screen: Cannot backup; HD
full. Went to Computer, and sure enough D: is full. Looked at contents and
found 27 backups of my Programs. They are all dated 4/25; they are all
compressed. Also found all of my Documents in as many files, all compressed
and dated 4/25.

How am I going to find my latest backup?

"It" states that there was a full backup performed on 3/10/08.

I am in a state of shock. Did try to delete one of them from 'way back; says
I can't because drive is full.

If I do find my latest backup, how am I going to delete the others?

Any suggestions: