some cheap arduino boards from ebay and amazon encounter problems while programming by showing the message that " the device not detected" or blah blah blah messages. it is because the drivers found from arduino.cc website is for ftdi chips on arduino board. but on cheaper clone boards ch340g boards are instead of ftdi chip. so you must install ch340g usb driver before connecting the arduino board. the step by step instruction is as follows.
Step 1: Now Let's Dance!
I cannot attest to the quality of the download files. I have tried it, successfully run a Microsoft Security Essentials scan and it does not trigger any issues with virus protection. Please proceed at your own risk!
Click here for the driver software
Before connecting the Nano to your USB port:
Download the “ch341ser,exe” file and run it.The software extracts about 8 files.
The software asks whether it can install the CH341SER.INF driver for the CH340 chip (Version 11/04/2011, 3.3.2011.11). Click INSTALL
A Windows message asks whether the driver has installed correctly. Click YES.
Connect your Nano.(or other arduinos)
From Control Panel, open Device Manager and Ports. If installed correctly you should see an entry “USB-SERIAL CH340 (COMXX)