Windows 7 still appears as an option in grub but when i choose it, it does nothing and goes back to the grub selection screen. I have tried boot-repair but it's still the same issue. Here's the log from boot-repair : http://paste.ubuntu.com/6468928/ .
windows installation diskthen select the
repair your computeroption before you go into the installation process.
After selecting windows repair option,it will take you to the next screen.In that screen select the
Then run the below commands,on it.
bootrec /fixmbr bootrec /fixboot bootrec /rebuildbcd
This will overwrite the grub installed in windows partition.
boot-repair-diskand click on the
recommended repairoption.Now it works.