This probelm should only occur with NT-machines because of a non available API function. You can avoid that problem by creating a registry entry as follows:

• Start -> Run -> Regedit
• Go to entry HKEY_CURRENT_USER\Software\VB and VBA Program Settings\ESM-Tools\CustomBirthdays\Options
• On the right hand of the window click with the right mouse button on a free area and choose New -> String Value
• Choose SetTimer as name and False as value

After a restart of Outlook® the problem is solved.

Advice: You should only work on the registry if you're familiar with that work. We are not liable for damaged systems because of a wrong registry entry. You should also keep in mind that the program is not approved for Windows® NT. That means that there are no compatibility tests in Windows® NT and there's also no support with problems.