Do NOT attempt to Delete a Windows installation if you have install Ubuntu via WUBI. It will leave your computer un-bootable.
Your WUBI install is, for all effective purposes, inside your Windows 8 install, and as such you should not attempt to delete it. You should copy all the data (your photos, documents, videos, etc.) from the computer and on to an external device (such as a USB stick or CD). You can then install Ubuntu 12.10 from (another) DVD or USB by burning and booting them. There, you can install a new Ubuntu installation, erasing both your old Ubuntu installation and your Windows 8 installation.
You may wish to follow these instructions to install Ubuntu on a separate partition.