Win 10 keeps freezing

Windows 10
Desktop
8GB Ram-64 bit

Please advise what other specs I should post. After last update on 9-14-17 computer works great until I actually try to do something. For example, I ran a software program that converts video files. This program usually works very quickly, but yesterday, it took around 12 hours to do what would have normally taken less than an hour. The bigger problem is trying to copy files from my C drive to an external HD. The copy process seems to start, but then freezes on anywhere between 0 & 2 percent.My computer is completely non-functional, and I'm trying to run a business. I don't even know where to begin. I've been researching for solutions for days, and everything I find is so incredibly complicated, I just can't believe that Microsoft would release these updates that cause such problems. Any guidance much appreciated.

Did I post something stupid? No ideas? If I need to restate my post or something, please advise. I was hoping to get help here. Thanks again.

Yes, I was having problems before the update... actually I hadn't had this particular machine on for awhile, so upon booting at the beginning of the week, it started doing a series of updates. I was hoping the last one on the 14th would fix everything, but alas, no. I will post my reports when I get back to my home office. Thanks so much, AndreTen!

1 -- Ctrl-Alt-Delete to pull up Task Manager gives error message in image, plus turns screen black. In other words, couldn't open Task Manager. I was able to "esc."

2 -- No yellow exclamation marks in Device Manager.

I'm hoping the error msg is related to the lagging issue. It took over an hour to copy 1GB from hd to ext hd... something that usually takes no time at all. Thanks so much for the help.

I scanned my machine using McAfee LiveSafe which came with Win 10. No viruses found. After scan, machine seemed to be running great. Again, I tried copying large file folder from C Drive to Ext HD. It was going great until it reached 19% then simply stopped. I was able to open Task Manager, and nothing appears to be eating up CPU (total: 4%) or Memory (total 20%). Everything else now running very slow again machine-wide. Thanks again for the help.

Have you done a scan with Malwarebytes? Or with any anti-virus prog other than the dreaded McAfee?

Look at your processes in Task Manager. Anything there that causes you to say "what the hell is that"?

Have you tried copying to that external via some other port?

Have you considered reverting to some prior state, as with Windows System Restore or perhaps a previously saved image file?

Have you done anything to check the health of your hard drives?

That error message appears to be legit:

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