XML database cannot be opened on Windows 2000 and Vista.
This specific issue was caused by PrintShop Mail 6.0 which always referred to a hard-coded version of MSXML. While this was resolved in a later version (6.1.3 and 7.1.3 at the time of this last edit), you can still resolve the issue on version 6.0 by downloading MSXML 2.6 from microsoft.com. More than one version of MSXML can work together, so installing it should not cause any issues with other software.