First off, by starting sharing, your computer IS asking remote users for an ID/password. The only problem is, it's trying to match the ID/pword to its local user listing, and you haven't created that account.
I think you're trying to password protect a folder(share), and that's not the way that WinNT works. You put an Access Control List (ACL) on a resource (printer/folder/file), and if the USER trying to get the resource is on the list, then they get the access specified. Typical ACLs are: Read, write, change, print, delete.
So for your scenario:
Create/share folder:
Apply an ACL to the share (NOT the folder), that looks like this:
ID: MYCOMPUTER\DeRusto Rights: Full Control
ID: MYCOMPUTER\MyBuddy Rights: Read
Now, to connect to this folder from any WinNT family computer:
net use * \\MYCOMPUTER\sharename /u:MYCOMPUTER\DeRusto * [\b]
enter your password (from the MYCOMPUTER machine) and hit enter.
Now, you're connected, and should be able to browse the folder/documents.
If you provide the account DeRusto, you'll be able to do whatever you want to the files in the folder. If you used the MyBuddy account, then you'll only be able to READ the files, and not modify them. Of course that give you the ability to copy the file, and modify the copy--you just can't overwrite the original.