Error in restoring a back up database to another database

I'm trying to restore db1.bak to db2 using restore wizard and it always fails saying "Database is being used" or something... I've checked all active session IDs using this query:

use master;
select a.spid, b.name, a.hostname, a.status from sysprocesses a
inner join sysdatabases b on a.dbid = b.dbid

And no one is using db2. Everyone is using either master, tempdb, and db1...

Why is this happening? Am I doing the restore process wrong?

Thanks in advance!