I just plugged my Arduino Uno into a new computer. I had used it before on an different laptop, so I have another program running. When I plugged it in, my computer started looking for the software, but I got an error message saying "Windows couldn't find driver software for your device." What should I do?
If your Uno has an ATmega16U2 USB to serial chip, such as the official Uno, then you can tell Windows to look in the drivers folder inside of the Arduino IDE installation folder.
If you have a clone Uno with a CH340 USB to serial chip. You can download the driver from http://www.wch.cn/download/CH341SER_EXE.html.