Windows 10: Reset the Screenshots counter to 'one'

In "Ask me anything" type in Regedit.exe and press Enter. When you open the Registry Editor, navigate to HKCU\Software\Microsoft\Windows\Current version\Explorer. Click the word Explorer in the left column to display all its actions in the right panel. Look for the Dword ScreenshotIndex, and right-click it to open that little dropdown. In it, click the top item, Modify. (see next screenshot)

That opens another window, and in the little value box in it, erase the old value and type in the new one, which is "01" (without quotes) then click OK, and you can then look again in the right panel at ScreenshotIndex, and you will see that its value is now showing 01. You can close Registry Editor now. You're done. But don't forget to go into your Screenshots folder and make sure you've removed everything in there, so it can begin again from one.