Clicking the File Explorer from the taskbar in Windows 10 will open the Quick Access folder. But to have and make file explorer open My PC instead of Quick Access by default, you need to do as follows:
1. Open the Filer Explorer on your desktop PC
2. On the top menu, go to the View tab and then click the Option to open the Folder Options window
(A quick shortcut: simply type File Explorer Options in the search box in taskbar)
3. Now, make sure you are on the General tab
4. The first options is: Open File Explorer to. Click the drop down menu and select the This PC option instead of Quick Acess.
5. From now on, clicking on the Filer Explorer button will open This PC by default.