How to re-enable Windows user options pop-up for newly mounted USB Flash drives?
Solution 1:
Go to:
Control Panel > Hardware and Sounds > AutoPlay
Or more simply, click on Start > Type autoplay and press Enter
Put a check on Use AutoPlay for all media and devices to make that AutoPlay popup-dialog appears for you again when you insert a external media device.
You might need to reboot your computer in order for this to work.