That driver is installed during the Arduino software installation. Something to try might be a full uninstall/install of the Arduino software. There may be a way to only deal with the driver, but I’m not that up on Windows operations.
Another thing that might happen is frying the USB chip on the Mega (voice of experience, here). When that happens, you could use a separate USB-Serial adapter to talk to the Mega over the Tx and Rx pins, even program it over that channel. That would use a different driver for the USB-Serial adapter. You could check whether one of the known repairs is applicable. Or replace the damaged Mega.
First thing I would do would be to delete the device from device manager, turn the Maslow off, reboot the PC, plug the Maslow into a different USB socket and power it back up.
If that doesn’t work: Using device manager, delete the driver and the device. Power down Maslow, unplug, reboot PC and reattach Maslow, then power on. You should be prompted to reload the driver. If not, that doesn’t necessarily indicate a failed arduino. Windows and serial USB is a can of worms.
Are you using a generic arduino or a genuine one?
What version of Windows? Please don’t say 8!
Have you got another computer you can plug your arduino into to test it? You won’t need the shield. Do you have a spare arduino you can use to test your PC?
If you observed normal electronic considerations when moving (power down PC and Maslow before disconnecting, connect and boot PC before powering up Maslow), the chance of is being toast is fairly low, it’s much more likely to be an issue with drivers and ports.
Let us know your findings and any other relevant info.
Sorry, I didn’t see this before replying… you plugged 12v into your arduino? That’s within spec and something many of us have done… and it looks like you’ve tried much of what I said, but my experience with my fathers windows pc and serial USB has been that it’s a nightmare. Windows 10 has improved things a lot.
Have you checked ‘hidden devices’?
Start, All Programs, Accessories, Right-click “Command Prompt” in Accessories and choose “Run as Administrator”
Enter “set devmgr_show_nonpresent_devices=1″ – without the quotes
Enter “start devmgmt.msc”
In the box that opens, select “Show hidden devices” in the ‘view’ menu.
I totally understand - with USB it can be tricky, the USB standard has a lot going on in the background. Most of the time it’s all transparent. I’m going to toss some simple troubleshooting suggestions here. Forgive me if I’m repeating others. First if possible try a different computer. 2nd try a different USB cable. If these are available to you it will narrow it down fast. Update us when you have time to check it out again.