Currently the only free version (------ed version) available on internet is Instrucalc 5.1 Plus. The download link to that is available in the forum if you search for Instrucalc. I have downloaded it and validated its calculation results against INTOOLS calculation module, Flowel 4, FirstVue, ValvSpeQ etc.
I searched high and low in the internet for a free (----ed version) version of Instrucalc 7.1. It is not available. There are several forums who claim to provide it. But they are all out to swindle you as I have realized painfully.
I do not know if Instrucalc 5.1 Plus works in Windows 7. I am still sticking to Windows XP. Most of these software's are compatible with XP.