Networking

I have a 2013 iMac (ElCapitan) with Airport WiFi. I also have a PC/Win10; connected wireless. The PC shows up as a device in Finder but is not connected. Is this a MAC problem or a PC problem? I can't connect because the system rejects any login/passwd I enter.

It's not a MAC problem but it could be a Mac problem.

A Mac is short for "Macintosh." It's not an acronym, thus it should not be capitalised.

To put it another way:
mac: a waterproof raincoat made of rubberized fabric
MAC: a data communication protocol sub-layer, also known as the Media Access Control
Mac: a brand name which covers several lines of personal computers designed, developed, and marketed by Apple Inc.

To establish networking between the PC and Mac, you'll need to find out what the workgroup settings are (on the PC). I would imagine (though I don't know for sure) that the password is your Windows admin password, but the workgroup connection is as I recall the key element. I'm pleased not to have to worry about this at home, nor at work for the last five years or so.

First thing on the Mac end open System Preference then click on Sharing then on File Sharing then on options (I hope it's the same word in El Capitan as right now I am in Mountain Lion). Be sure both both AFP and SMB have a checkmark by them. That does the Macs end. Windows 10 is a bit different but I have for sure been able to connect to it.

I am booting a W10 machine here and will get back if anything special needs to be done. Be sure Network Sharing is enabled though in windows.

Have you ever been able to network your Windows 10 system to another Windows system?

Just checked and I was able to log into the Windows 10 system from my Macbook Pro with 10.11.2. Be careful to put the exact username you are logged into with windows 10. Not the machine name. Windows 10 is a bit different in that way. When you do log in you should see your Windows 10 users folder. At least that is what I see here and was able to open that and go into my account and see all the documents and downloads ETC on the windows system.

On the PC, I was able to access the iMac by selecting an icon on the desktop named "this machine". It opens up a display off everything on the PC including the network. I could select "network/walters_imac". I was able to open documents on the iMac. On the iMac, I can see the PC (on the left margin of the Finder window under "shared"). When I click on the PC name a window pops up showing an ID and asking for a password. I've used every password I have used in the past 5 years and it rejects them all; I could explain this better if I could use screenshots (Snagit)

If you have all the settings the way I described above, you are entering something wrong. What are you entering for the login name? What type of Login are you using on Windows 10? Your Outlook login or a normal User login? Exactly what are you entering for Login?

You can on your Mac just hit Command+Shift+3 to take a shot of the whole screen or Command+Shift+4 to select the area you want to capture. If you have issues uploading it here we can help you.

Are you sure on the user name you are entering? I have had many issues in the past due to entering that wrong.

Also you missed my question. Are you using a Outlook account to log in or a user name?

A username. I have also changed the user name, but that didn't help (trying to work with 2 unknowns).

Since I didn't know what the logins/passwords were for the PS Win10, I purchased a program that would allow me to reset it.($20). That worked out fine, and I was able to setup the Admin account and several others. Then I was able to gain access to the PC from the Mac using one of those accounts. (My trouble started when the hard drive on the PC went south and I had it replaced). Thanks.