Your initial problem description is very confusing...
1st: I have no idea what port 80 and 21 have to do with Mapping a drive from Window.
Port 80 is used for HTTP access/server
Port 21 is for FTP
SMB is a different port, probably 445 but within your LAN, and it is use to map drives.
If you are accessing all of the ports mentioned above from within your LAN/Home network, there is not need to touch the router at ALL.