I setup all my computers with a master admin user name and password the same - this is the renamed Administrator account. But I then setup an Admin account on each computer with a unique user name and password.
That way when I want to connect to another computer I have a different user name and ID for that computer to log-in.
Since you are in a workgroup and not a domain, your accounts on the different computers are different even if named identically.
The account on the main computer maincomputer\myname is different from the account on the small computer smallcomputer\myname. I have found that using the same user name and the same password is likely to cause issues with some programs.
I setup my accounts like this:
When I want to connect from one to the other - I setup the share - give the Users group Full Control security rights.
From the other computer I will map a drive to the share - and connect with a different user name.
If I am connecting from the Win7Dell to FSX on the Win7Alien - then when I create the mapped drive on the Win7Dell - I use the Win7Alien\User123 ID and password to log onto the Win7Alien computer.
I'm not sure that makes a lot of sense if you haven't worked with accounts and passwords.
The key is to understand that your ID on one computer is not the same as your ID on another computer even if both belong to the same workgroup. There are two parts to a computer ID - the name of the computer holding the account, and the name of the account.
@ PawPaw's house - near KADS, Addison, Texas, USA