Installshield and register DLL's ?!?

I have the following problem with installshield projects:

There are a number of DLL files that need to be registered when I
install the application. On some machines, the installshield procedure
says: "Installshield could not self-register XXXXXX.DLL".

I did the test on a Win95 machine, so normally I have full access to
the registry (there are no limitations as in WinNT in case you don't
have admin rights).

The DLL files that need registering are:
- MSVCRT40.DLL
- MFC40.DLL
- CFX32.OCX
- OLEPRO32.DLL

In most cases problems occured with files MSVCRT40 and OLEPRO32.

I'm aware that this is possibly a beginner's question, but I can't
find it in the Installshield help files...

Thanks in advance,
KDM.