System process reading disk 100% and making the system very slow

I found out that the hard disk is 100% utilized. In Task Manager, the process that utilizes the disk the most is ESET Service. If I open Resource Monitor there are many instances of the System process that are reading the disk, not writing it. I have two partitions on my disk - one for the system and the other one for data; the extensive disk reading is done for Pictures (I assigned a folder with pictures, about 140 GB in size, to the system My Pictures folder) on the data partition.

I am not running any tests in the ESET Endpoint Antivirus software and it seems to me that the high disk activity starts when I do not do anything and just e.g. browse Internet or look at something. So, it feels like Windows is doing something, but I have no idea what it is and how I can influence it. If it were disk optimizations I think I should see also disk writes, not only reads. Could it be that Windows is doing something automatic with Pictures, Documents, etc.?

I wonder what is going on - I dislike the fact that something is going on with the hard disk, making is 100% utilized and making other work very slow and non-responsive.

I think I found out what was going on. I accidentally opened the Windows Store app named Photos and the high disk activity has been a problem since that time. To stop the activity, I had to remove the folder My Pictures from Sources in the Photos app's settings. I think the Photos app was somehow cataloguing all pictures, which I do not need or want.