Recently i installed Ubuntu alongside windows 7 on my Dell 15R 5537. Initially everything worked fine but after some update perhaps; windows stopped working. On selecting windows from the boot menu, it would show a purple screen, however i could hear windows boot and its start screen. Googled for days but did not find an exact solution. Here is what I did
First try doing this
On the grub menu highlight the windows menu item using the keyboard and then press 'e' to the end of the line that begins with "set root= *******" add 'quiet splash' so that it becomes
"set root= ******* quiet splash"
now press ctrl + x
Does it solve the problem? If it did now you proceed to make the change permanent
Start ubuntu
press ctrl + alt + t to open up terminal
type 'sudo gedit'
in the editor navigate to /boot/grub/grub.cfg and open the file
In the file select the menu entry for windows and copy it
Now open the file /etc/grub.d/40_custom
Paste the menu entry that you copied previously after the comments on a new line
In the menu entry add the "quiet splash" as done before
Save the file
Now run
sudo update-grub
Reboot, enjoy!