I am using Windows 8.1 and successfully turned on and programmed a Nano yesterday. I declared victory by loading the routine that causes the LED to blink on and off for a second each time. Then, I copied the Blink program, changed the delay times to 3000 ms (instead of 1000 ms), uploaded again and sure enough, the LED was blinking 3 seconds on and 3 seconds off.
I have been very careful with the board regarding ESD and general protection both electrically and mechanically but today, for some reason, I cannot upload to the board. I get the following error message:
"Arduino: 1.6.3 (Windows 8.1), Board: "Arduino Nano, ATmega328"
Sketch uses 1,030 bytes (3%) of program storage space. Maximum is 30,720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.
avrdude: ser_open(): can't open device "\.\COM1": Access is denied. "
I have tried assigning different numbers to the COM port and have tried different USB ports in my computer.