Solution for semi-bricked Pro Micro/mini-Leonardo clones:
The OP's question is ambiguous to as the exact Arduino device in question. My answer applies to the "Pro Micro" or "mini-Leonardo" since these Clones usually use the default Leonardo boot loader, not the modified Sparkfun version.
Note the the Pro Micro doesn't use an external serial to USB chip at all. So the "CH340T USB" argument doesn't apply here. The USB is directly wired to the ATMEGA chip in this case as it has built-in USB 2.0 support.
I've made two projects with these: I gutted an old keypad replaced with a Pro Micro Clone and turned it into a extended keyboard so I could get F13 to F24 keys plus some others, then a custom game foot controller (to 'Q' and 'E' lean in FPS shooters).
Problem, I went to update my Foot controller sketch and after over a year later I forgot my Arduino IDE settings. This time I must have used the wrong setting like "Sparkfun Pro Micro" 3.3.v 8Mhz when your clone is probably like mine a 5v 16Mhz model.
When I uploaded the sketch it failed and apparently corrupted the program Flash header or something.
The original code was still running (on pedal press my LED lit up) but the device now showed up as "..missing USB device descriptor.." type message in the Windows device manager.
Fear not, it's probably recoverable like it was for me.
First of all realize you DON'T set in the Arduino IDE the board to "Spark Fun Pro Micro", simply set it to the default "Arduino Leonardo".
That's the right board setting for these clones. The Sparkfun bootloader IS different, as it says on their site. If you uploaded their bootloader then it might work but that's an experiment for another time.
Now you will need to add a reset button to the right hand side of your board (with the micro USB plug pointing up). The pins are next to each other and are clearly labeled.
I found a mini-switch just right to fit into the header pins from my parts box. In a pinch you can probably solder two small insulated stripped wires as a makeshift switch, but it might make the following step harder which is timing related.
If you plug your Clone Micro back in, notice if you press the switch the Clone Micro will show back up as a Arduino Leonardo on a COM port for about 8 seconds, then fall back to the bad USB ID thing again.
Now in your Arduino IDE create a NEW sketch. Which will create a minimal program that you'll need to restore your Clone back to working order.
Hit the reset switch again and quickly in your IDE preset the "port" to the COM port that shows up. Don't worry it will remember it after the device falls back again.
Now comes the hard part. Unlike a real Sparkfun Micro you can't double tap the reset button for extra time, you only get the 8 seconds period.
In the IDE click the "Upload" button, wait about a second, then hit your reset button.
If all goes well, you will see the typical flashing programming LED success lights and you will have restored your Clone Micro! This might take a few tries depending on your timing.
The thing is to press your reset button slightly after you click the Upload button (or CTRL-U) else you will miss the time frame of the special bootloader reset phase.
Basically this is the directions given here, with a little more details:
The OP got some opinionated and pretty toxic responses for an open-source hardware device. Some common sense notes on the morality and ethics of buying Chinese clone devices:
First of all, at least this is not nearly as bad a situation of the Chinese fake chips, arguably the real scourge of the Electronics parts world.
Without spending too much time on the legal ramifications and not being a lawyer, it looks like most of the Sparkfun stuff is CC licensed. Although doubtful the license if for their original or modified software/firmware.
From the Arduino site:
"Arduino is an open-source hardware and software company". So the clones are apparently not illegal to buy in the USA (if this is the country of contention).
The reason a lot of people buy the clones is you can buy around three or more of them for the same price of just one Sparkfun Micro.
I've been an electronic hobbyist since the late 70's and part of the equation for me is getting a few extras because there is always that chance I'll fry something despite double if not triple checking my wiring.
I can make a project plus have some spares for the next time.
I wouldn't use it in anything mission critical, but so far the Clone has been working fine for me as a hobbyist.
These things being said, I'm a big fan of Sparkfun. They are a relatively small USA company that makes fun innovative products with helpful Youtube "how too" videos, etc. I'm all for supporting them.