How do I repair a Ubuntu WUBI disk? 

Issue: your installation of Ubuntu by the WUBI method has become corrupted and won’t boot.

Fix: boot the machine from the Live CD, open a terminal, and type:

sudo fsck /media/Data/ubuntu/disks/root.disk

Where your Ubuntu installation is on your DATA partition on your laptop.

If your root.disk is on your “C” drive, change this to the name of your “C” drive. Eg if your C drive is “Fred”
it would be:
sudo fsck /media/Fred/ubuntu/disks/root.disk

If this doesn’t work, then try this:

sudo mount /dev/sda5 /mnt
sudo fsck /mnt/ubuntu/disks/root.disk

Bootinfoscript can be used to determine the location of your wubi file.