You don't need to drop database. After you migrate DB,you can either create logins with same username and password and map the logins or if you are doing for muliple dbs and logins then i would suggest you to search for "Transfer logins from one server to other server" kb article
dropping the database didn't work either I would like to delete from both and start again but it doesn't let me drop the user from the database (that was restored from the backup) what else can I do?
To migrate logins - lookup sp_help_revlogin and install that on the source system. Use that procedure to generate the script to create the logins on the destination.
This script will create the logins with the appropriate SID, which will then map to the users in the database correctly and also creates the logins with the same password as on the source system.