Problem Restoring Backup File in SQL 2005

Hi Experts! Could you please help me in working out for the method on using BT in two computers?
I attempt to exchange my databases from one PC to another, but I received an error “There was a problem restoring a backup file: C:UsersgarryDocumentsBlackthorneBackupsbtdatabackupsql003bak.
The current database may be in use, you may need to restart the program before attempting to restore it.” when opening database on other computer where the database is created.
I can see that it is working even if I got an error, but I am thinking that it might break my database in the future.
I am running SQL 2005 Express in my Windows Vista with BT 04.07.018.
Please send me some solutions.
Thanks.
