Here is what I have read about mscomct2.ocx. I have not verified anything.
mscomct2.ocx is an activex calendar control. You can obtain an up to date version of mscomct2.ocx from http://activex.microsoft.com/controls/vb6/mscomct2.cab.
32-bit windows, such as XP, have mscomct2.ocx in c:\windows\system32.
For windows 64-bit you need to put mscomct2.ocx in a different directory, c:\windows\syswow64.
In conflict with the above paragraph, I have also read that you need to put the MSCOMCT2.OCX in the same folder as your program. Eg. if your program is in C:\MyApp folder, then put the MSCOMCT2.OCX file in C:\MyApp folder too.
Once the mscomct2.ocx file is installed, it needs to be registered. You can use the Microsoft Register Server (Regsvr32.exe) to register a 32- bit .ocx file manually on a 32-bit operating system. You must run regsvr32 as admin.
In conflict with the above statement from support.microsoft.com, this works on a 64-bit system as long as the ocx file is in the syswow64 directory.
If you have obtained the file and registered, yet still have problmes, it might help to first unregister, then register:
regsvr32 /u mscomctl.ocx