I have a Duemilanove with a ATmega328, which I tried to connect to a Windows XP computer using a USB cable. I've downloaded the IDE and it runs.
When I first connected the USB, the power light on the board came on and the pin 13 light began to blink repeatedly 4 times rapidly. Windows began the new hardware dialogue, but since it couldn't identify the hardware I canceled out of the process and went to review the hook-up procedure.
But now Windows won't recognize that anything has been attached. No new hardware dialogue comes up. The My Computer window doesn't identify anything there. In the IDE, the Serial Ports command is dimmed. When I go to the device manager, as some help recommends, I don't see a line for Ports. I still get the blinking light on pin 13.
I'm ready to start my big adventure but I'm off to a tough start. How do I get this computer to see the Arduino?
I suspect you have to go into your windows device manager and remove the driver that you originally tried to install but didn't finish correctly, and then window should 'see' the board as a new device when you plug in it to the PC and asks you about installing a USB driver for it. Be sure you follow the correct driver installation instructions as your older board uses the FTDI USB drivers not the newer drivers that most arduino boards use.