Login Failure to computer on network - Why???

I have 4 computers that are networked together using XP and Vista. On one of the computers (B), when I try and log into computer (A) thru My Network Places, I get a message that it is inaccessible, then Login Failure: Account currently disabled.

I think I know what the problem is, since it happens from another computer (C) as well, what seems to happen is that computer (A) has a account name and password, so from computer (C) , I first have to open Network Properties, locate the icon for computer (A), double click on it, then a box comes up to put in the account name and password. After I do I can access computer (A) from (C).

Unfortuneately when I try this from computer (B), I can not get it to open the password screen.
What am I doing wrong, and how can I remove the necesity to even enter the name and password for that computer.

If I map the drives, then am I mapping the whole drive, or just a folder, and when I right click the drive, it gives me an option to map, but where do you have the option to reconnect at login??