This one was a real head-scratcher, it took me a lot of time to find out what was wrong and how to fix it. As usual, the final fix was extremely simple, but as it is unfortunately often the case when it comes to performance issues, this might or might not be the definitive solution for you.

The symptoms were these: an Acer E15 laptop had become extremely slow after upgrading to Windows 10 using the built-in updater provided by Microsoft (it was previously running Windows 8.1 with no particular performance issues, even if the CPU on this series of laptops is definitely not among the best in the market). So at least this was a pretty clear clue that something went wrong with the update itself.

I am talking about really bad performance: up to 10 minutes for a reboot and up to a couple of minutes to launch any application. Even writing something in the search bar took several seconds.

Looking at the Task Manager, I could also see that the disk usage was at 100%. The application using most of the disk was usually Windows Defender, although sometimes some other application would take this spot, so it wasn’t completely consistent.

What I tried before finding the solution

I am including all these because they worked for some people, so you might find them helpful. Some of these had a minimal impact on the performance of the laptop I was trying to fix, but if you read the comments in these links you can see that they helped completely solve the issue for some users:

The solution

Even after doing all the things listed in the previous section, my disk usage was still around 96-97%, so there had been no noticeable improvement.

What finally solved it for me was configuring Windows 10 for best performance rather than for best appearance. After the upgrade to Windows 10, the default choice had become Let Windows choose what’s best for my computer, which basically enabled pretty much every visual effect and anymation.

Needless to say, Windows made a very poor choice at choosing what was best for this computer. Luckily, selecting Adjust for best performance under Control Panel > Adjust appearance and performance was all that I needed to do to bring disk utilization back down to a normal level, and to consequently solve all the performance issues that had arisen after the upgrade.