I've installed the Arduino 0004 IDE on my XP machine with no problem. The USB board talks to the PC just fine. I've updated the Java VM to the latest version and installed the USB driver from the Arduino distribution on both my Win2000 laptop and my XP desk machine. The Laptop with Win2K just won't talk to the Arduino board no matter what I do. The RX/TX lights stay dark and the Java exceptions are all I get.
Anyway, I can work with my XP PC just fine, but I am very curious why my Win2K laptop and the Arduino won't play together. I'll swipe my wife's Win2K Toshiba laptop and try that too just to see what happens.