Windows 10: I need help getting Windows computers to see each other

I have four computers on a network, three are Windows 10, the 4th is Windows 7. Computer 1, my main computer can only see the Windows 7 computer. Computer 2 can see 3 & 4 but not Computer 1. Computer 3 can only see computer 4 and computer 4 can't see any of them. I especially need for computers 1 & 2 to see and communicate with each other. I have file and printer sharing enabled on both of them.***Moved from Gaming and Xbox / Hardware and network / Xbox on Windows***

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windows xp installation and dual core am

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