I recommend that you download Ubuntu 12.04.5 iso image or Xubuntu 12.04.5 or Kubuntu 12.04.5, your choice, and also download the executable, wubi.exe from the same page. Place both files in the same folder and install Ubuntu with wubi.exe, no Internet connection or additional download needed. If possible, choose another partition to install Ubuntu instead of the partition where Windows 7 is installed.
It is better this way because you will be able to use all the software that no longer work in Ubuntu 14.04.
And if you really need to make wubi.exe work with Ubuntu 14.04 you have to use a simple command after first reboot, that is after you started wubi installation in Windows and it asked you to reboot the system to continue installing Ubuntu 14.04. Basically, you have to press the key e at first boot prompt for Ubuntu and look for this line to edit it:
linux /boot/vmlinuz-3.2.0-68-generic root=UUID=B21CF9B91CF978A5 loop=/ubuntu/disks/root.disk ro
and replace it with
linux /boot/vmlinuz-3.2.0-68-generic root=UUID=B21CF9B91CF978A5 loop=/ubuntu/disks/root.disk rw
As you can see, all that is needed is to change ro to rw after section loop=/ubuntu/disks/root.disk from that line. Next, you can press F10 to boot and hopefully, this way, Wubi will finish installing Ubuntu, but after you get there and find yourself facing your new Ubuntu desktop, you should edit the same line(s) in grub.cfg, a file which is located in ~/boot/grub/grub.cfg. To edit grub.cfg use this code in a terminal window:
gksu leafpad /boot/grub/grub.cfg
or
sudo nano /boot/grub/grub.cfg
and look for the same line:
linux /boot/vmlinuz-3.2.0-68-generic root=UUID=B21CF9B91CF978A5 loop=/ubuntu/disks/root.disk ro
and also for this line:
linux /boot/vmlinuz-3.2.0-68-generic root=UUID=B21CF9B91CF978A5 loop=/ubuntu/disks/root.disk ro recovery nomodeset
and replace ro with rw so they look like this:
linux /boot/vmlinuz-3.2.0-68-generic root=UUID=B21CF9B91CF978A5 loop=/ubuntu/disks/root.disk rw
and
linux /boot/vmlinuz-3.2.0-68-generic root=UUID=B21CF9B91CF978A5 loop=/ubuntu/disks/root.disk rw recovery nomodeset
Once again, all you have to do is to change ro to rw after this section loop=/ubuntu/disks/root.disk so you stop experiencing problems each time when trying to boot into Ubuntu.
You can use this solution or you can simply press e at each boot prompt for Ubuntu and edit that line and change RO to RW every time you want to use Ubuntu. This is a very useful command since you'll be forced to upgrade your system to yet another kernel version (Update Manager will take care of that...), and after that you'll have to edit file grub.cfg again because of the new kernel and replace ro with rw again in grub.cfg.