Before files such as ActiveX controls can be used by CitectSCADA (or any other program), they must first be registered with the Windows operating system. Controls are usually registered during installation of the program (i.e. Microsoft Visual Studio)  but can also be registered after installation using the Microsoft Registration Tool called REGSVR32.EXE. In CitectSCADA v5.21 REGSVR32.EXE was installed in the Citect\User\Example\ActiveX directory. In CitectSCADA v5.30 and later REGSVR32.EXE is installed in the Windows root or C:\<WindowsRoot>\System directory.

To register an ActiveX control or DLL file, please follow these steps:

1.  Open a command prompt:  Start menu | Run... | type "cmd" | click OK
2.  Type:  regsvr32 <FilePath>

Example:  regsvr32 c:\winnt\system32\mscal.ocx

To unregister an ActiveX control or DLL file, please follow these steps:

1.  Open a command prompt

2.  Type:  regsvr32 -u <FilePath>

Example:  regsvr32 -u c:\winnt\system32\mscal.ocx

Unregistering ActiveX controls will remove their entries in the ActiveX tool list without having to delete them. You can think of it as removing them from the active-duty roster.