Go here for the update:
http://v4.windowsupdate.microsoft.com/en/default.asp
click on Scan for updtaes.
As far as the MBox the monitoring functions of it are garbage, you have to always adjust the input/playback knob to monitor everything, it's very annoying. I suggest either running the outputs of the MBox to a small mixer or a monitor switching device like the Samson C Control and running your monitors out form there.
Edit: Also, some folks have had success getting rid of the distortion by uninstalling the MBox and reinstalling it in a different USB slot.