Windows 8.1 file explorer is Super slow

The most common problem for the "This PC" delays is networking. A network drive that was once connected is not present.

If you boot your PC with the network cable disconnected, then the "This PC" will open instantly if you have this issue.

This is because when you start your PC with networking enabled the "This PC" shortcut execution shows you a dialog with all of your drives and other system elements. It also invokes a parsing agent that looks for all those previous network locations to "fire them up" and "prepare them" for your viewing pleasure.

You most likely have this delay caused from orphaned network locations if when you start your "This PC" it first shows a few icons then after a few seconds, waits and then shows a status bar. At the same time the status bar starts, the "Items count" appears. This is the local "This PC" telling you how many items there are and that it is done opening the "This PC" window. This is where the bug comes in. Now it is going to have a status bar while it tries to connect up to all those previous network locations. The rest of the time it is networking and parsing to find those previous network locations.

I have not found a way to turn this parsing off yet. I am still looking. My PC did not do this until I used it for 3 weeks and discovered some network locations. Turning on and off sharing and network discovery does not seem to change "This PC" network parsing and discovery issues.