Eu uso siga os seguintes passos no Windows para trazer o botão "Install Install Inside Windows".
Mount Ubuntu 13.04 ISO Using demon tools. (In My Case, Virtual Drive is G:)
Then open G: in CMD
Now Use Following Code
'G:\>wubi.exe -force-wubi (This is For 32bit Machine)'
'G:\>wubi.exe --force-wubi (This is For 64bit Machine)'
'This Code Work for me, In you case It want, You can try alternate code from 32bit for 64bit and for 64bit use 32bit code. Its work 100%'