Symptom:

Cannot open DST files, in EmbroideryStudio, by double clicking them on them in folders, or as email attachments.

Solution:

*** Please note that this solution requires modifying the registry, and should be done by someone who is knowledgeable, and capable of working within the Windows Registry.  An incorrect change to the registry can be catastrophic.  We highly suggest backing up the registry before making any changes. ***

1.) Open Regedit: 
Type “Regedit” in Windows Search.  Right-click and choose “Run as Administrator.”

2.) Fix the open .DST issue by changing the following registry keys:
Changing the value of “HKEY_CLASSES_ROOT\.DST” from “DST_auto_file” to “ES.Document”

3.) Delete the key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.DST

4.) Reboot the workstation