My Arduino is unable to connect to Windows 10
Assuming you're using the classic Arduino UNO -- the Atmel ATmega328 Electrical Characteristics table shows Absolute Maximum ratings of 6.0V Maximum Operating Voltage, and also &quot;Voltage on any pin except RESET with respect to ground&quot; of -0.5V to VCC+0.5V (i.e. -0.5V to 5.5V assuming that VCC=5V). So applying 12V to any of the Arduino digital or analog pins will permanently damage the microcontroller, no way to undo that damage. The only chip on the Arduino UNO board that can take 12V is the input of the linear regulator, everything else must be 3.3V or 5V logic levels.
For pretty much any logic level boards, 12V is dangerous (not to you but to the board), so you need to be careful. When wiring up &quot;high&quot; voltage, connect the load before connecting the power source, and disconnect the power source before disconnecting the load -- otherwise waving around a &quot;high&quot; voltage wire could contact something it's not meant to contact, and damage can occur. (I put high voltage in quotes here, because usually &quot;high voltage&quot; means 48V or more, which is unsafe for humans to touch.)
Depending on exactly which model of Arduino you have -- and if you have access to an electronics technician or are one yourself -- it may be possible to repair the board by replacing the ATmega328 chip itself. You'd have to make sure you ordered exactly the right part number including the suffix, they come in various types of pin/package sizes, and there is also an ATmega328p variety. And Arduino UNO has both a 28DIP and 32TQFN board variants. But given how the Arduino boards are sold at bargain prices, it's more efficient to just swap it with another Arduino board. Even if you take this opportunity to practice your soldering skills, you can never completely trust this damaged board again, because there could be damage to the other chips on the board as well (such as the USB to serial interface chip).
Furthermore, if this was your only Arduino board, you can't just replace the ATmega328 with a blank, factory-fresh ATmega328, because it needs the bootloader firmware image to be loaded before it will work with the Arduino IDE. Without the bootloader firmware, the only way to get firmware into the chip is by using an device programmer connected through the SPI port. It's possible to configure a second Arduino board as a device programmer to reload the bootloader into the other board, or else you'd have to see if sparkfun or adafruit sells a preloaded ATmega328 with the bootloader already loaded.