Microsoft recommends that you connect USB devices directly to the Macintosh computer and not through a USB hub, if you can. If your Macintosh computer does not have sufficient USB ports available, Microsoft recommends that you use a powered USB hub. Microsoft does not recommend that you connect USB devices through keyboards that have USB ports.
To turn on USB support in Virtual PC, follow these steps:
On the Window menu, click Virtual PC List.
Click the virtual machine that you want to support USB devices.
Note After you turn on or turn off support for USB devices, you must restart the virtual machine if it is currently running. You cannot make changes to virtual machines that are part of a Saved State.