A small inexpensive used laptop running XP might be your best answer - my guess is that it might more than difficult to get it working in Win 7. Another thought is upgrading to 4D - I had 3D and upgraded to 4D a long time ago and 4D works perfectly in Win 7.
Also - you could call Pfaff/Viking directly or a large dealer (their software techs are one in the same) and see if they have any suggestions. Good luck - it is always a bummer when you get something new and that "breaks" something else!!