Another Login after restoring database

Hello all,
I have created a backup of a database and Restored as a new database in another machine.
Primary login of the database was X , now after restoring as a new database I dont want X as the login name i want it to be Y ...
how to do that ?

I can create other login as y and Give necessary premissions...but the Problem is i have to manually issue all the permissions to the new user which i feel is a time taking process.

Please let me know about it..

Thanks and Regards
saiI am not sure but u can try this :
script the login and user for the database in question,after generating the script for the user X,delete the the user X from the database ,Replace the user/login name X from the script with Y and run the script on the database.
I think this should work after some enhancements in the script.|||Use roles!

Or sp_change_users_login SP