To reduce the size of your database:
1.Check the number of users registered for the database, and delete users if needed. The acceptable number of users varies, depending on the performance of the server and the network.
2.Remove any temporary files
3.If your projects have outdated history information, remove it.
4.Delete any unused files and projects in the database.
5.If there are projects that are not interrelated, move them as needed to separate databases.
To shrink a file after it is allocated, you need to use the SHRINKFILE command:
DBCC SHRINKFILE (N'FileName' , size in KB)
More info check : http://msdn.microsoft.com/en-us/library/bb508963(v=SQL.90).aspx