I have 4 versions of IDE on my Vista laptop - but thinking about it I've never actually connected a board with 8U2 or 16U2 USB/Serial adapter since I stopped using a Duemilanove for testing(all custom boards now, I don't torture myself with those ridicously small chips).
More than likely you are just missing the Uno driver.
Can you connect to the board, do the Settings: Control Panel: Add New Hardware and browse to the Uno file:
C:...\Arduino-1.0.1\drivers\Arduino UNO REV3.inf as an example path?