If you have previously used the right click and opened with path oyourjavaw.exe then you will need to remove the following registry key.
[-HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerFileExts.jar]
Then run
C:>assoc .jar=jarfile
C:>ftype jarfile="C:path oyourjavaw.exe" -jar "%1" %*