Hi all, I just crawled out of a pitfall that others might fall into. I've been using all sorts of usb-to-serial converters in different usb ports and when I plugged in my (USB) Arduino it showed up as com17. I could select it from the Arduino IDE but when I tried to upload my program I got an error saying something along the lines of "/dev/com17 does not exist". (On Windows XP!)
The solution is to give it another port number. I didn't know you could do that, but it's simple:
Select My Computer, right-click, select Properties On the Hardware tab select Device Manager Open the Ports (COM & LPT) group and select the USB Serial port where the Arduino is Right-click on that and select Properties On the Port Settings tab clicke the Advanced button At the top of the page there's a drop-down menu labeled COM Port Number. Select a lower port number there, even one that says "in use" - but select one that is not actually in use, of course. My guess is that anything below COM16 will work.