Control Panel (while viewing Large Icons.)>>>
Network and Sharing Center
Top left, click on Change advanced sharing settings. Click the dropdown arrow for the type of network you chose to use, previously.
Make sure these settings are applied:
Turn on file and printer sharing.
Use 128-bit encryption to help protect file sharing connections
Turn on password protected sharing
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Then on the machine you want to share from, make sure the folders needed to be accessed are shared with permissions for "Everyone" without the quotes. (If you need help with this, please let us know. You actually have to type Everyone and then grant the type of access you want to give.)
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Then make sure the accounts involved on all machines actually have a password set. It is easiest if all machines involved have the same user/password set but surely not the only way.
What you DO NOT want to do is have the same user on 2 different machines that have DIFFERENT passwords.
If you are sharing between different user names, while mapping a drive, you can set it to use different credentials and also remember them upon all Windows reboots.
Anything else needed, please let us know and good luck.