Try the fix at this site:
Drizzle Info WIKI
they say that:
<span class="ev_code_BLUE">Windows 7 On Windows 7, Teledahn does not work properly. You can fix that by right-clicking on your "UruExplorer.exe", choosing "Properties", then selecting "Compatibility" and enabling compatibility mode for Windows XP SP3. This however triggers some problems with videos copied from Myst V - so if you converted these ages, you should now remove the files "direboWithAlpha.bik" and "mystWithAlpha.bik" from your "avi" directory.</span>
Hope that helps