I recently bought an Uno and found, as a number of others apparently also have, that there's a problem with the Windows 2000 driver that blocks efforts to upload a sketch into the Uno via the USB port. I've found at least 2 workable solutions to this problem, have described them at http://arduino.cc/playground/Main/UnoWin2k
and am still experimenting with other tricks. If you've got any other techniques for using an Arduino under Windows 2000 that you've found and are willing to share, please forward them to me at firstname.lastname@example.org
and I'll incorporate them into the article for any other fellow Win2K users out there. Thanks.