Recovery Drive

Low disk space is showing on my revovery drive (D) what do I do if anytning. Or what will happewn if D drive is full?

If you are talking about the drive containing the System Restore points, it merely deltes the oldest one to make room for the newest

I expect Windows Backup is storing backups on your recovery partition.

It does that because it is the only drive it can find [ apart from the Vista partition(s) ]

Either use external media to store your backups - or turn it off.

You can't afford to damage the recovery partition.

See Step 15 here:
http://www.vistax64.com/tutorials/100133-backup-files.html