I got a Win7 64-bit machine in April.  Since I had never installed the final update on my old machine, I went to eon and saw that warning.  I figured the data loss they warned about had to do with the program itself.

I had UAC turned down, and Vue 6 installed with no problems.  However, when I installed the update (went with the next-to-last I already had), it got to 95% and stopped.  As I watched, all of my desktop icons started to disappear.  When I finally got control back, everything had been wiped out!  I mean EVERYTHING.  I had to use the recovery discs to reintall Windows.

Be forewarned.

John