I did a clean install of Windows 10 Home x86_64 just last weekend. I decided to install Avira Free(v 18.104.22.1688 - 7/15/2015; Search Engine v 8.03.42.56 - 8/12/2015), since I've used it on both Windows 7 and 8.1 without any problems. And up until Friday night(8/14), I had no problems using it with Windows 10 either. I decided to do start a manual scan, which normally takes about 25 minutes, and I booted up my other laptop to check for updates and do a few other things. About a half hour later, I checked in on Avira, expecting to see a summary of the scan and then shut it down. Instead, the progress was still at 32%. At that point it was late and it wanted to go to bed, so I cancelled the scan and shut down. This morning, I checked for definition updates then started another scan, this time watching to see what was going on. The scan progressed at a normal pace until it hit about 29%, when Avira began scanning the contents of C:\Windows\WinSxS, and right there is where it began to crawl, taking about 10-20 seconds to scan each individual file. Given the sheer size of WinSxS (7.87BG/14,424 folders/82,095 files), I now understood why it had only progressed to 32% when it should have been finished the night before. Does anyone else using Avira have the same problem, or have any clue to what's going on? There is one very important coincidence that I discovered today: On Friday afternoon KB3081438, a cumulative update to Windows 10, was automatically downloaded and installed. Does anyone have any idea what this update did as far as WinSxS is concerned? Is this a clue or merely a coincidence? Just one more thing: Please do not suggest using another antivirus program as an answer. I chose Avira because of the fact it has the highest detection rates out of all the free antivirus programs available as of 2015, and I really want to solve this problem instead of side-stepping it. Also, please do not suggest posting this problem on Avira's user forum. Been there, done that. No answers as of yet, at least nothing useful.