Try the following:

1. Ensure that Handheld Contact is closed.
2. Open Windows Explorer.
3. Go to: C: Program FilesACTACT for Windows (or whatever folder you have ACT! installed to).
4. Look through the files for an app called ‘MachineConfigUpdater.exe’.
5. Run this.  It may just flash on the screen and seem like nothing happened.
6. Go back to the desktop and try launching Handheld Contact again.
7. What happens?  Does it open up?  Do you get any other error messages?