Thanks for posting back your specs. Though it's somewhat incomplete, it's a start.
Network troubleshooting can be tricky. Did you try neemo's suggestion from POST #2 on changing your DNS ip addresses? This often solves the problem or at the very least will help us to identify it.
Here are some other easy things to try:
1.) Can you hook up your computer directly to your Cable Modem or DSL Modem Ethernet port via a hardline Ethernet cable? (for example: a Cat5 or Cat6 Ethernet cable) In other words bypass your wifi router if you have one. Plug directly into your Ethernet ISP-provided box's Ethernet port. This may require you to physically move your PC to another room in your house (which I know is a pain), but if your PC then connects to the Internet your Windows networking, RAM, hard drive, are probably ok.
2.) If #1 fails, your PC configuration has failed.
This can be caused by Windows system file corruption, virus/malware infection, or failed hardware such a RAM memory stick(s) or a failed hard drive! Since your ISP has already had a look at your Modem and probably performed an end-to-end diagnostic, their suspicion that the problem lies in your PC is correct. At this point, you'll need to perform hardware and then software troubleshooting to resolve the problem within your PC. I'll give you a link on how to do this.
HERE'S THE TROUBLESHOOTING LINK: Windows 10 - Unclickable Task Bar
3.) If #1 passes (works), then the problem could be in your wireless driver or the device has failed completely. It could also be from a virus/malware infection. Nowhere in this thread has anyone suggested that you scan for viruses yet. You should do this with the built-in antivirus you have installed on your computer. Additionally, download the free
MALWAREBYTES from Malwarebytes.org which checks for spyware viruses that most AV programs can't catch. Detect/disinfect any all virus/spyware virus infections from your PC and proceed to #4.
4.) After scanning for and removing viruses from your hard drive, the next thing is to have a looksee at your Wireless adapter driver in Device Manager. Does the listing under the Network Adapters heading show any icons such as the yellow triangle warning or the red-x warning next to your wireless adapter entry? [D-link DWA-140 Wireless N adapter]. If it does, you'll need to set a Restore Point and then uninstall the driver. Go the D-link support page and download the most current driver for your wireless adapter. Disable your AV program, and install the new D-link driver. Make sure it has no warning icons next to it in Device Manager. If ok now, unplug your Ethernet cable from your Modem, plug in your wifi router back to the modem, and attempt to wirelessly connect your PC to the Internet via your wifi connection. Post back result. If it works, your D-link driver was messed up and now works again!
5.) If #4 give you no good result, it could be your wifi adapter that failed.
To test for this, ask if your friend with the identical PC build would mind helping you a bit. Remove your D-link adapter from your PC and take over to his place. Set a Restore Point on his PC, and uninstall his wifi adapter driver (D-link or other). Visit the D-link support page and download the latest driver onto your friend's PC. Install the D-link driver and plug in your D-link adapter to his PC. If you get the Internet through his wireless connection to the Internet, your D-link adapter is Ok!
And the problem still resides elsewhere in your PC. To find that, have a look at this
TROUBLESHOOTING LINK: Windows 10 - Unclickable Task Bar
6.) Next, you need to troubleshoot your PC further to find the problem there. Use the link in #5 above. to do this.
You need to troubleshoot this problem, like any network problem with the fewest number of devices connected on your LAN as possible. Like the old song, "1 is the loneliest number", it's also the best way to troubleshoot your network, with only 1 computer connected to your Modem or Modem/Router combo. To clarify, you got no error messages with only the 1 computer connected to your Modem or Modem/Router combo, correct? Then when you add additional computers back into your Modem by plugging back in your Router and plugging in those additional computers to the Router you get the error message right? Can you tell us whether you have 2 boxes or not, as referenced in bochane's post above? Do you plug your extra computers into the Modem ports (RJ45 Ethernet), or do you plug your Router into the Modem (WAN port), and then plug your extra computers into the Ethernet ports (RJ 45) on the Router? We can't see what you have, unless you can send us a photo with your smartphone, so you have to be specific on what you have in front of you. We aren't psychics!
Did you try items #2-#6?? Your response is very confusing and cryptic.
The cost is about $150-$300 US; so we'll certainly understand if you can't afford that. However, it's an option if you follow all our troubleshooting suggestions and cannot resolve the problem on your own. 
