I have an application that uses mscal.ocx. It works with Windows 7 if I register with Administrative privileges. However, after registering on Windows 8, 64 bit machine, I get the "failed to load activeX control" error. How can I get the mscal.ocx control to work on a Windows 8 machine?

I had this happen on a Windows 7 machine and had to copy over MSCAL.ocx from a machine that had Office 2007 installed (its stored under %ProgramFiles%\Microsoft Office\Office12) and copy it over to System32(or in your case %systemroot%\syswow64) and then run regsvr32 %Systemroot%\System32\mscal.ocx (again your case it would be "%Systemroot%\Syswow64\mscal.ocx).  Once it was registered it worked.  I haven't tested this in Windows 8 but its worth a shot.

Tried it on windows 8.1, still doesn't work.