Chris is probably refering to configuring Win7 Pro with XPmode (a virtual install of XP on Win7). It works great for legacy apps which are not compatible with Win7 - you can even have shortcuts to the XPmode apps on the Win7 desktop so the end user doesn't even realize it is running inside XP. However, XPmode being virtual doesn't have direct access to the hardware including USB ports - it is virtualized by the host OS and this is where the testing needs to come in. Even though Vixen will work fine in XPmode you might trade off one problem (plugin working) for another (dongle not working)...
Chris, if this is what you are thinking, I'd be happy to test once I get my dongles built. But if one of the other members who have the hardware and Win7Pro want to do it and need assistance I'd be happy to PM some directions.