If you have shared folder or drive in a PC but it can not accessed from other computers, then check this:
1. Open Control Panel --> Administrative Tools --> Local Security Policy.

2. Select "Local Policies" --> "User Right Assignment" --> "Deny Access to this computer from the network..."
Remove any User in that box.

3. Select "Local Policies" --> "User Right Assignment" --> “Access this computer from the network”.
Make sure "Everyone" exist.
1. Open Control Panel --> Administrative Tools --> Local Security Policy.
2. Select "Local Policies" --> "User Right Assignment" --> "Deny Access to this computer from the network..."
Remove any User in that box.
3. Select "Local Policies" --> "User Right Assignment" --> “Access this computer from the network”.
Make sure "Everyone" exist.