Another PC on this network has the same IP address question

Last night received this popup on my desktop pc: "Network Error- Another computer on this network has the same IP address as this computer. Contact your network administrator for help resolving this issue. More details are available in the Windows System event log."Contacted Comcast support and was told this is a Microsoft operating system error and to contact Microsoft? - if so why would the error popup tell me to contact Comcast?
Has someone hacked into my account or network and if so what can be done?
Any suggestions or advice would be appreciated.
Frank

Do you have more than one computer or device on your home network? Could include computers, tablets, smart phones, IoT devices, etc. If so, then likely one of them has a duplicate IP address.

Could be your next door neighbor.

Log into your router and look in the router logs to see which devices have been connecting via your router. Blacklist everything except what you know is yours. This won't hinder a determined hacker, but it will block most people.

To protect your network from a neighbor:

• Make sure you have encryption turned on in your router. I believe that WPA2 is the current standard; don't go less than that -- i.e. don't allow WPA or WEP.
• Make sure that there is a password on your wireless network, so that devices have to have a password to connect to your router.
• Make sure there is an administrative password for your router, to keep unauthorized people out of your router's setup screen.
• Remove the default WPS password. (WPS is when you push a button on the router, then on the device, so that the device can connect to the router without having to do it the old-fashioned way.)
• Pick a non-descript name for your wireless network. Don't call it "FranksWifi", because your neighbors would recognize that it is yours. Call it "footballfan" or some other name that is not easy to figure out that it's your network.

It must be another PC local so from cmd prompt type
Ipconfig /all
Do it on every PC until you find which PC has it one PC must have a static IP as dhcp won't issue two the same

Thanks for the responses and suggestions Jim and samuria - I did a scan using the app "Whos on My Computer" it listed 5 devices - 4 of which I could readily identify. See attachment. Of concern was a voiced comment that kept repeating..."Unknown Computer" Not sure exactly what that means or what to do about it. I note that there are devices ...001,...002....003....004 and 006. Wondering why ...005 skipped?

I believe what you mean by "001,...002....003....004 and 006" refers to the last number of each device's IP address. It might be easier to follow if you look at it like this: 192.168.1.1, 192.168.1.2, 192.168.1.3, 192.168.1.4, 192.168.1.6. I wouldn't worry about 192.168.1.5 being missing from the list.

The two Dell listings both begin with "F8.B1.56". Dell has registered that as one of their network adapter MAC address series. So any network devices starting with "F8.B1.56" is a Dell device.

Apparently Hon Hai Precision has at least two MAC address series registered: "90.4C.E5" and "70.18.8B".

The Netgear device is either a network device or the router itself. Obviously Netgear has registered "20.E5 2A".

The question I would have is, why are there two Dell devices and two Hon Hai devices? Your computer is obviously a Dell, and it apparently has an Ethernet network adapter and a wifi network adapter, and both are connected to the router. Either that, or you have two Dell computers. Not sure about the Hon Hai devices.

To find out what you are dealing with, go on each computer, open a command prompt, and type ipconfig /all [ENTER]. You will see all MAC addresses listed on the screen; you can then compare to what is shown in the above listing. Whatever you cannot account for, you can log onto your router, go into the setup area, and tell it not to allow those MAC addresses. Doing this will keep out most people, but a determined hacker would not be stopped by this.

Where is the unknown device? I don't see it in your screen clip.

Thanks Jim, you are correct in delineating the devices. I have the following devices - 2 identical model Dell desktop pc (mine and my daughters); I have an emachine laptop (possibly one of the Hon Hai Predision devices), a Netgear router, but the second Hon Hai is a mystery. Could possibly be an LG tablet that my son gave to my wife last year which see has never used? Will run ipconfig /all to check on the laptop and the tablet.
Thanks for you patience with an 86 year old novice.

Frank