I’m assigned the task of deleting some databases from some server.
Deleting a database is easy: http://msdn.microsoft.com/en-us/library/ms177419.aspx
Seems like there is one service for each database in control panel>administrative tools>services
How can I remove those?
I take it you are referring to instances.
You can just use add/remove programs and select SQL Server 2005. It will give you a list of instances you can select to delete/uninstall.