Running Windows XP, Arduino UNO, clone. The board has been working fine, but then I had a short circuit in wiring a new sketch which totally shut down my computer. BLAM !! but no smoke! It recovered with no damage but when I plugged in the USB cable, the 'on' light came on but not the blinking light on the board. When I tried to compile/upload a proven sketch I got the error message, "BOARD AT COM 4 IS NOT AVAILABLE". Did I blow the board or, if not maybe the CH340T chip? And, btw, my com4 does not show up in my ports listing even after I re-installed the driver.
All help greatly appreciated by this guy only 3 months into Arduino.
If after a short circuit that passed enough current to shut down the computer, the COM port does not display, I would suspect that you've damaged the board.
Have you checked with other USB ports? It's also possible that you damaged the USB port. I've had hubs that stopped working on certain ports as a result of abuse like that.
Sometimes these can be fixed, but as you're relatively new to Arduino, and don't seem confident in working with electronics, this is probably not worth pursuing, particularly since clones are pretty cheap.
I can easily replace the --328 chip if you think other chips on the board are serviceable. What do you think?