Hi, Well the problem is back this morning. If I click on File Explorer, it will eventually open, but it might take a minute or two, usually it opens instantly. I also notice that when this happens, I also can NOT open UPDATE AND SECURITY. If I click on Start / Settings, all the other 8 items open instantly, such as System, Devices, Network, Personalization, Accounts, Time, Ease, and Privacy. But when I click on Update and Security, the next page opens, but none of the items on the left side will open such as Updates, Defender etc. Sometimes when this happens, I check Task Manager, and the Disc activity is OK. No problems there. When this happens, if I RESTART the computer all will be fine after it boots up. This problem also only happens during the first half hour or so after Startup. The rest of the day it seems OK, but not 100% sure about that. I will pay attention to that from now on. I got this Dell OptiPlex on Feb. 12. It has the I7 4790 processor, and works great except for that problem. It boots to the desktop in 25 seconds. It had Windows 8.1 on it, but I did a CLEAN install to Windows 10 from a Disc I had created. Just about ready to start over with a format and another clean install, but afraid the problem will be back after I spend several hours doing another install. Any other suggestions ?? Can I do a REPAIR with that disc I made, even though I already did that SFC / SCANNOW. If so, will I loose anything I installed since, like all my pictures, music, etc. Thanks, for any suggestions, Mike