How can I easily see which COM port is used by Arduino? I'm rather disappointed because I just bought arduino and I am unable to upload any projects. The error I get is:

avrdude: ser_open(): can't open device "\\.\COM3": Časový limit semaforu vypršel.


Can be translated as:

avrdude: ser_open(): can't open device "\\.\COM3": Semaphore time out


Am I expected to brute-force all available ports to see which one is reserved for arduino? How can I, on Windows 7, quickly determine which port to use given that the IDE for some reason can't do that for me.
Start | Control Panel | System | Device Manager | Ports (COM &amp; LTP).

Watch the list change as you plug / unplug the Arduino. The new port is the Arduino.