Hello, you can use Mathcad 5.0, 7.0, 8.0, 2001 and Mathcad 2001i on Windows 7 Pro/Ent/Ultimate 64 bit.
(Most likely also Mathcad 2000)
But you need the XP-Mode for Windows 7.
After a direct installation of Mathcad 5 and 7 failed, I used the XP-Mode.
This will allow you to use the software on Windows 7.