Explanation of each server role in sqlserver 2000

Fixed server role description
Sysadmin performs any activity on SQL Server. This role's permissions span all other fixed server roles.
Serveradmin configures the Server Range settings.
Setupadmin adds and deletes the linked server and executes some system stored procedures (such as sp_serveroption ).
Securityadmin manages server logon.
Processadmin manages the processes running in the SQL Server instance.
Dbcreator creates and modifies databases.
Diskadmin manages disk files.
Bulkadmin executes the bulk insert statement.

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Db_owner database owner
Db_accessadmin database access Administrator
Db_securityadmin database security administrator
Db_ddladmin database DDL Administrator
Db_backupoperator Database Backup Operator
Db_datareader database data reader
Db_datawriter database data writer
Db_denydatareader database rejects Data Reading
Db_denydatawriter database rejects data writers