Vista - low disk space warning

I have a new DELL machine with Vista installed on it. I attempted to run the
Vista "file" backup utility on Drive D: (Recovery) - not realizing at first
that was a small partition. The backup failed due to lack of space. Since
then, a low disk space warning pops up repeatedly. The drive has only 6MB
free so the error makes sense. The total drive space is 2G. The space I can
see actually used on the drive is under 1G - I can't find files using up the
other 1G.

It seems like the failed backup file is taking up space on the drive since
the warning never appeared before the backup attempt. I've searched for the
backup file or folder but have not been able to find it. Does anyone know
where/how it can be located?

Thanks.