That D partition was not set up for backups. You were not supposed to use it for anything or change anything on the small D partition. It is on the same hard drive as C so it is useless if the hard drive fails. That was only to store the factory image for recovery. You cannot recover anything on it now and you cannot use the recovery image. Buy an external hard drive for backups. This mistake (which is an honest one that many users made since it was unfortunately called Recovery) is less possible now. The Recovery partition on the newer windows 7 computers is hidden so the user doesn't see it. The only thing to do now is order a vista disk from Dell here: support.dell.com/.../backupcd_form  US customers only. 
I have an Inspiron 518 purchased in Feb. 2009 directly from the Dell online store. Recently I am getting a low disk space message for Recovery Disk (D:) which is the partition set up for backup and restore. (I did not receive CDs for reinstallation of the factory settings; it is all on Disk D:) Vista Home Premium was factory installed. When I click as instructed to solve this problem, I get the MS Cleanup utility. Running this utility makes no change whatsoever in the available space. My understanding is that the earliest backups and restore points should be automatically deleted to make room for new ones. This, obviously, is not happening. I can find no information on this partition, and the backup procedure was changed in April of that year. Can anyone help me with this? I suspect that the partition never worked properly or possibly has become corrupted. Any suggestions will be greatly appreciated! 
Inspiron 518 Recovery Partition