Restored database size I have a large (90 GB) database. About half of the space is taken up by two tables that are no longer used. I intend to truncate these two tables and as I understand things this won't free up the space (on the disk) assigned to this database until I shrink it. I don't want to shrink it at the moment.

There is an overnight backup process. Will it be possible for me restore this database to a server that only has 50GB space free or will the restore create a 90GB database that needs a shrink?
Are you using the compression function in SQL 2k8? If so then it should work.

I would personally restore this database onto a Dev/Test server and just carry out the scenario you have stated and see what size a full backup is.