You can : msdn.microsoft.com/.../aa176794(v=sql.80).aspx but you may not, shrinking the database is not always a good option and you need to look into the details before actually performing this step directly. Shrinking the complete database which is small in size is most of the time work but shrinking the database which are very large in size is not always good. I would say check which file is big .mdf or .ldf based on that you may shrink the specific file if there is really some space to release.
For CRM I would say check the recovery model of the database if that is set to simple or not, if that is not what is the reason for keeping the recovery model to any other than simple and if there is no reason take a full backup , change the recovery model to simple and then shrink it will release the unused space (if there is any) immediately.
How to shrink a database (Enterprise Manager): msdn.microsoft.com/.../aa176794(v=sql.80).aspx
Thanks,
Mohammad