Need help - can't open Mathcad 3.1

[nevillemac]

For some time I have been unable to open Mathcad 3.1.  I twice requested help via the Academic Case Logger, and once via a customer support address, but I have heard nothing.  I am running Windows 8.1, 64byte.

The problem is that all attempts to open 3.1 fail & generate the message: "This application requires ... .NetFramework,Version=v4.0.” Installing 4.0 and its 4.6 “replacement does not remove the message even when all existing copies are deleted.  Also  deleting and reinstalling 3.1 does not work.   Regedit.exe shows "Release REG-DWORD 0x0005c615 (378389 Finally, Prime, Viewable Support & PTC Diagnostic tools. ASP.NET 4.5 is ticked in Programs & Features.

Does anyone know of a fix for this?

[LucMeekes]

Are you sure that you've installed the prerequisites (.Net and what else) also as 64-bit?

And then there is this: Re: Mathcad Prime 3.1 Crashing

Success!
Luc

[VladimirN]

That is, it turns out that some time ago Prime 3.1 will work properly? If so, then this is due to some Windows update packages.