What does the computer do after you install the CH340 driver and then plug-in the USB cable connected to the Arduino?
If it's working correctly, you won't see anything on the desktop or lower right status area. To see if the Arduino has been assigned a port, you'll have to hit the control panel, then Device Manager, and look at Ports (COM & LPT). (The image is from a Win 10 ultimate machine but it behaves the same as my remaining Win 7 box.)
If the driver isn't loaded correctly, or there's a problem with a particular USB port, you'll get an error pop-up in the lower right of the desktop when you connect the Arduino. Sometimes, using a different USB port is enough to 'force' Windows to reload/reconfigure the driver - that will usually make it work in all USB ports.
73, Andy, KG5RKP