You can use the Shift+Right Click Button on the Keyboard to get the option in the Windows......du it while selecting the file....
This behavior can occur if the registry key that handles the command is altered or damaged.
This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs.
Use Registry Editor to examine the file association key for unknown file types:
The "default" value for this key should read:
C:\%windir%\rundll32.exe shell32.dll,OpenAs_RunDLL %1
If necessary, modify the value to match the value shown here.
I hope this fixes ur problem