Occasionally the list of ActiveX controls shown on the Tools\ActiveX Controls dialog is incomplete. Some of the controls installed on your system are not shown.
This might be caused by a bad registry entry. MSM-Workstation constructs the list by enumerating through subkeys of the following registry key, looking for those that in turn have a subkey named "Control":
HKEY_LOCAL_MACHINE\Software\CLASSES\CLSID
It expects subkey names to be no more than 38 characters long, which is the length of the {}-bracketed representation of CLSIDs. If it encounters a longer name the enumeration terminates. The most common cause of this problem is a faulty registration procedure for a COM object on your system.
Use the following one-liner in the WS Command Window to list all the CLSIDs that WS's dialog will see:
s c=$&MSMDEV.RegBeginEnumControls f q:c="" w !,c s c=$&MSMDEV.RegNextEnumControl
Use regedit to review CLSIDs that follow the last one listed by that line. Look for the overlength key and try to identify the originating component. Uninstall it, or if you're feeling brave, delete the rogue key.
For example, several Windows 2000 users have seen a CLSID of "{FC9E740F-6058-11D1-8C66-0060081841DE}f" — notice the extra "f" at the end. Its single VersionIndependentProgId subkey appears to belong under the preceding CLSID, "{FC9E740F-6058-11D1-8C66-0060081841DE}".