For many of these, Win-7 will recognize it automatically and load drivers with no further to-do. Some off-brand stuff may come with its own driver CD to load. You should know that there is a lot of junk/knock-off/counterfeit USB-serial stuff out there that doesn't work very well. Even if you get a driver to work, they frequently have comms problems.
Download the latest version of USB SERIAL CH340 drivers according to your computer's operating system.
Personally, I'd return it and get something better. Air-link, IOgear, SIIG makes good stuff. Other brands may be OK as well if they use the FTDI / prolific chipsets but its hard to know.
There are some long threads here discussing the problem. After messing around with a few bummers, I finally went with a PCI-E 4X serial board from SIIG. Works perfectly all the time with Win7-64 Pro.
If you are like me and ordered a cheap arduino nano clone from a chinese website like aliexpress or banggood, chances are that they come with the cheaper CH340 USB to Serial chip. This is a cheap chip that manufacturers exploit to make the clone a lot cheaper. This can also be a downside. For me, being a mac user, I had a real hard time finding drivers etc for it. In the end I found some drivers, which were pretty good and I finally could get a blink sketch uploaded.
I now want to share my experience for future buyers so you can get it working a lot faster. If everything is done correctly and there were no errors appearing. You should be able to restart your arduino IDE and see the port. For my mac it is usually like above in the picture but sometimes it changes. You will also notice that once in a while (maybe 1 time of 3) you will get errors when uploading but you do not have to care, the code will usually upload either way.
I hope this tutorial helped you and remember that the CH340 chip is a bit complicated and it may also be used in other cheap arduino board clones. Thanks for reading and once again, I hope it helped you. Just a quick comment re Linux installation - year is now 2019 and Arduino IE is version 1.8.8. Tip 1: don't use apt get to install Arduino IDE on Ubuntu, Elementary or other Debian/Ubuntu distros. The repos do not have nice new versions of the IDE. Download instead from site and follow instructions. Tip 2: do not forget to add the current user to the dialout group.
'sudo usermod -a -G dialout $USER' Tip 3: In the IDE under tools make you may need to set your 'Processor' to ATmega328P (Old Bootloader). Depending on the generation of the CH340 and esp. If you get message 'programmer is not responding'.
Comment: Because of the situation with the repos in Tip 1, I did not even try to install the IDE from the openSuSe repos. I downloaded the IDE from and used that in my openSuSE machine. So, I have Arduino Nano CH340x working on Mac OS (Mojave), Ubuntu 18.04, Elementary Linux (forget version) and openSuSE Leap 42.3 Malachite. It was not at all necessary to install drivers or make them on the Linux machines - but I did install them for the Mac. Downloaded from the Chinese site.
A bit of a challenge as I don't read Chinese - but the little cloud symbol with a down arrow kind of gave me a clue. Info on Github is really good too. Also see Good luck. As a linux user (Ubuntu / Linux Mint 17) I had difficulties with the cheap Nano with the CH340G chip getting it to work properly - the upload of any code didn't work at all. Of course I had installed the Arduino IDE (apt-get install arduino) but was not able to program the Arduino nano. Then I found in a german web article that from time to time you have to reinstall the IDE after a system update of the kernel, so that the serial USB interface works again. I didn't do it but my Nano started to blink when connected to the USB port so I thought it couldn't be out of order and should work anyhow.
After connecting it to USB in the /dev folder you should find a file called ttyUSB0 or ttyUSB1 or so. In my /dev folder I had found it.
So I started again, setting the Arduino IDE platform tool menu 'Tools' and 'Board' to 'Arduino Nano w/ATmega328' (in my case) and 'Tools' 'Serial port' to '/dev/ttyUSB1' (in my case). Ubrt 2300 v4 programmu. Now, the code from the 'Blink' example in the IDE could be uploaded to the Nano board as it should be and the LED started to blink.