Hi, Kitty.
Some brands are proprietary. Bernina is and it sounds as though that also goes for Viking.
I read at PatternReview where a Bernina owner was able to use the San Disc Cruzer brand by removing the stick's U3 program. I have no idea what that means, but I use this brand as is with my Babylock.
San Disc Cruzer is not expensive, maybe you could try one. I got mine at Radio Shack (1GB) for around $8.00.
I ready doubt if anyone representing Viking will share this information.
If you cannot get a satisfactory response here, try posting your question at - http://sewing.patternreview.com/SewingDiscussions/forum/25
I checked Yahoo Viking Group and there is little to no activity at the site.
Pattiann