I have an SL 50 and am running Windows 7 Professional. When I went to the Rescue and Recovery function in ThinkVantage there are no back-up files shown which I can delete.
I can, however, view the back-up files but there are no buttons for me to check in order to remove these files. I am stuck with 120GB of backups out of total capacity of 280Gb.
Try deleting the backups one at a time, with the most recent one first.
As Rescue and Recovery makes cumulative backups, it is not possible to delete "in between" backups. Please try the following; delete the last backup on its own, and then if more backups are required, work backwards, so always start with the newest first. After deleteing the newest on its own you should be able to delete multiple backups.