My Arduino Mega 2560 is showing up in Device Manager fine. I can see that it is set as COM5. The arduino IDE software doesn't detect it at all. That's all I know.
Make sure the device manager doesn't show any error flags with the port driver. If it does, uninstall the port driver and reinstall the driver with "hardware installer" in windows. The "search the computer" selection in the genie will detect the arduino list of drivers if your Ardu IDE is installed correctly. Use it. Leave "have disc" unselected.
Arduino can't "see" the Windows port unless the board is connected to the computer. Then you have to adjust the ardu/tools/serial port assignment by clicking on it.
I suggest shutting down the computer w/o the board attached before you do all this. Start a new installation cycle from the ground up. It seems to clear out any conflicting previous attempts.
change the usb port if that's not help
just restart your pc, then try other port
that's happens when you not have the last universal usb driver,