Process Explorer: https://technet.microsoft.com/en-us/sysinternals/processexplorer.aspx
(Read the description for more info and another way of fixing it)
DONT MESS AROUND WITH SYSTEM32 FILES OR ANY OTHER FILES YOU DO NOT KNOW/UNDERSTAND THE ORIGIN OF, IF YOU DO SO YOU MAY DAMAGE YOUR COMPUTER. I cannot be held responsible for any damage you do to your own system.

Okay so I have found a (temporary) solution. This solution will DISABLE tumbnail generation for .webm files; meaning that you won’t get a thumbnail for any webm files but COM Surrogate won’t be hogging CPU because of that.

Here’s what you do:

1. Go to this site and download the full package:
https://www.codecguide.com/download_kl.htm
2. When you’ve downloaded the installer, run it and check the available options to your liking. (I’d advise you to just let them be how they are). When you get to this screen:
http://i.imgur.com/3ma1KVY.png
Uncheck .webm and click next and install the codec.

Like I said, this will disable thumbnail generation but it will solve the problem of League replays (.webm files) causing issues.

If you are not able to delete the file you can just stop the COM Surrogate task with task manager, or boot into safe mode.

I faced this problem myself and while there are some good explanations on several sites, I decided to make this video since sometimes I’d rather see what to do than follow instructions by text, and I don’t think I’m alone in that.

Please take the opportunity to connect and share this video with your friends and family if you find it useful.