sysadmin permission to my user is looking fine. some of my findings are like this. Sql server provides 2 types of authentication to the users.
1) windows authentication with the domain name
2) sql server authentication.

My user is having only sql server authentication.Because we need to work with the remote databases.

so here what i want is I need to lock the access permission to one of my user not having sysadmin role.

I think sp_grantlogin and sp_denylogin will work only for the windows authentication mode users.
So how to lock my user having sqlserver authentication.

Hope you got my point.