Computer Help and Support

If it goes poorly, reinstalling Windows 10 should not pose much of a problem.

So, before you uninstall McAfee, you should make a Win 10 installation flash drive -- just in case.

* Follow these instructions to create the installation drive. (You will not have to enter a product key license number.)

https://www.microsoft.com/en-us/software-download/windows10

Then, try uninstalling McAfee. See what happens. It may go through several reboots.

If Defender does not come on by itself, you should be able to enable it. If it still won't enable, you have the ability to reinstall Windows.

* When attempting to create the installation media, you might get a message asking if you want to upgrade the computer immediately (which bypasses the use of the flash drive). You might consider doing this. But first, stop this process. Uninstall McAfee, then get back to the process.

I think it best to ensure McAfee is entirely off the computer before reinstalling Windows (which we hope will not be necessary).

And, needless to say, make sure you have all your personal files backed up before doing any serious operations.

One of the nice things about Win 10 is that it will install all your drivers for you.

The advice given to you by Orwell above is very good.