No grub menu after installing Ubuntu
You're probably missing the file below when you installed Ubuntu.
/boot/grub/core.img
So you need to use chroot to have it fixed. Take a look at this site
Yes this is also happened to me you can take a look on Can I install Ubuntu inside Windows?
you can try this where d is your iso image drive and run this command
D:\wubi.exe --force-wubi
I believe what you said was that you used a Wubi installer and afterwards you are unable to select Ubuntu as your operating system.
The answer has been provided here: No boot option after Ubuntu install