Marie:
Your problem may also be in the OLE2 field of the record containing the ActiveX control on the form. If the problem is that the ActiveX control is not registered, you'll be alright with just a runtime installation. However, if you have several team members doing development on both Win9x & NT platforms, you'll find that the path in OLE2 will be as follows:
Win9x - c:\Windows\system\msacal70.ocx && MS Calendar control
WinNT- c:\WINNT\System\msacal70.ocx

You may also run into version problems if your target machine has Office 2000, Windows Installer Technology, etc. Windows MAY try to use a newer ActiveX control. On my Win2000 box, I can't have msacal70.ocx and mscal.ocx (MS Calendar Control 9.0) both registered.

HTH