Ghost 14 - Backup drive ran out of space

I've been using Ghost 14 since early 2008. I happened to notice that the 750GB drive used for backup has only 3 GB left. When I try to delete the oldest recovery point set the operation fails (it looks like it creates a temporary file that will be larger than 3 GB)

 

Three recovery points sets are shown. The earliest has 24 recovery points and uses 436GB.

 

Any help would be appreciated.

 

Thanks.

OS Vista SP2