I'm not certain that this will work with WUBI but it works with regular installs.
Boot from your live CD or USB. On the splash screen click try Ubuntu without installing.
Open the home folder with he launcher. To the right of the window that opens you will see your hard disk listed as "(xx)GB Filesystem". When you open that filesystem you will be able to see all the folders in the hard drive. One of the folders will say "home" if you can see the Wubi files.. when you open that file you will see your username, open that file and all your personal files should be right there.
If this works just save the files to a usb then you can reboot into windows and use the "Add Remove Programs" to uninstall Wubi.
Just make sure that when you do a full install you select the option to "install alongside Windows" if you select the other one it will wipe your Windows installation.
The complete directions form Ubuntu's website are here....Installing Ubuntu Desktop
I have to add here, if you boot Ubuntu from a USB you will need another USB to save your files to, the USB with Ubuntu installed on it will not be accessible while you are booting from it.
{edit} I just stumbled across this answer to a similar question, it tells you how to attempt repairs of you Wubi install if you want to try that. https://askubuntu.com/a/130440/65969 {edit}