On some computers, I've found that the "2.0" version of MSCOMCTL.OCX has been added to the ActiveX KillBits list, and thus the control won't be allowed to load or run--even in design view. Updating to the "2.1" version will resolve this, and is the recommended solution.
In critical cases, where you have to run a program "now", or you don't have access to source code, or the control is used 400 times in a large modular project, you can use a "big hammer" method and update the registry to re-enable the control:
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WARNING: Editing the Windows Registry in the wrong way can mess up your computer big time. If you're not sure what you're doing, please leave it alone, or get some schooling before you proceed.
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The clear the KillBit:
- Run Registry Editor (regedit.exe or regedt32.exe)
- In the left-hand panel, navigate to key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility{BDD1F04B-858B-11D1-B16A-00C0F0283628}
- In the right-hand panel, double-click on “Compatibility Flags”, change the value from Hex 0x400 (Decimal 1024) to 0, then click OK.
- Launch the application that uses the "2.0" version of MSCOMCTL.OCX; it should run as designed.
The ActiveX KillBits list is intended to give Microsoft the means to disable controls that are deemed to be a security risk, and they've designed the mechanism such that the ActiveX KillBits list will be re-applied to the system at seemingly random times, in addition to when an Update is installed, so you'll need to plan for re-applying the registry change. Making a registry merge file works pretty well, but it's not something you want to do everytime the app runs, because it's not a quiet process (there are ways to do this quietly using Windows Scripting, but you'll have to learn that on your own). The KillBit is checked only when the control is requested by an application, so you're safe from resets once the application launches and loads the control.