On your keyboard, press the "WINDOWS" and "R" keys at the same time.
Then type this: cmd
And press enter, this will open a Command Prompt window.
Now drag and drop your stronghands-qt.exe onto this window, the text link to the file should appear, now add the following text after a space: -zapwallettxes
It will appear similar to this
C:UsersUser> C:stronghands-qt.exe -zapwallettxes
Now press enter.