I had no issues with my Dell Desktop upto yesterday. I have got 2 network cards installed in the PC. One is a Dell Wireless card and there is no problem with this. I can connect to the internet if I enable this card. I usually connect to the router with a cable as this is a more stable connecttion with the Realtek PCIe GBE Card. I have unistalled and reinstalled the drivers and there are no conflicts. When I look in device manager under Network adapters there is the dell card and the realtek and also about 8 wan miniport adapters that I have tried to unistall without any success, should these wan miniport adapters be installed on the pc or are these causing the problem.

Yes - they could be using interrupts settings or other address settings... if not in use then taking them out will tell the tale.

Remove any drivers for the mini port wan cards and any other software if you do not intend to use them

All removed still doesnt work.

Suggest you boot a LIVE Boot Distro (CD, DVD, USB. SDCard ...whatever will boot on your machine) that contains generic drivers for your hardware and see if it works, and rule out hardware failure. Many Linux distros can boot live and autodiscover network hardware. There's a Windows 10 trial that might also work.

If the Live Boot works, and without issue over a period of time, then it's a software issue.

If the Live Boot fails it unfortunately won't help.

Hope you've also tried other cables, other router/switch ports. Failure could be anywhere along the chain. Added any new software, or updates prior to the failure?

When you look at your router LED where you are plugging your network cable coming from your desktop, is the LED on or off?

When you look at your router config page, do you see if your desktop is linked to the router?

Are you sure that the problem is not the cable itself?