"sp_spaceused" procedure is really handy to get the updated information about space usage by database or tables.
I combined the same with another very useful procedure "sp_MSforeachtable" to get this information for all user-defined tables.
If you see any problem with the information then just change the last parameter and set it to TRUE (FALSE in the script). That will update the space usage and then report updated details.
Thanks
Mohit Nayyar
http://mohitnayyar.blogspot.com