Do the previous episodes still work?
If they do maybe the prefs.prop got corrupted while your computer crashed.
Try renaming it. A new one should be generated the next time you start the game.
You should find the prefs.prop in the folder
%USERPROFILE%\Documents\Telltale Games\The Trial and Execution of Guybrush Threepwood
%USERPROFILE%\My Documents\Telltale Games\The Trial and Execution of Guybrush Threepwood
depending on your windows version.
In order to find out why your computer crashed in the first place a dxdiag log could be helpful.
Windows XP: Go to your start menu and click on run. Type in "dxdiag" and hit enter
Windows Vista / 7: Press the windows key on your keyboard or
click on the start menu. Type in "dxdiag" and hit enter.
Now click on the button that says "save all information".
It will prompt you to save a file. Save it where you can find it.
Then zip the file
and attach it to a message.