Thank you all for the reassurance on migration of Mathcad 15 to Windows 7. Since I am just about to take that step, I checked this forum to see if there were any pitfalls. Unfortunately, I misinterpreted the problems experienced by some (and solved here) as representative. Rather than the apocalyptic heading about "end of the line," I really should have asked contributors whether installation on W7 generally goes smoothly. Apparently it does.
For 25 years, Mathcad has been my primary computational tool. I feared that my hundreds (thousands?)of research calculations, tech reports and a book, all written in Mathcad, were headed for the dust heap. Well, ultimately, I suppose they will be, but not just yet it seems.
Thanks again.