How to install Ubuntu 12.04 within Windows 7 with a CD image of ubuntu (without use of an external CD/USB)?

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http://askubuntu.com – The wubi installer that comes with Ubuntu 12.04 doesn't allow one to install ubuntu within windows. I downloaded the Wubi installer available here Ubuntu Windows Installer This howerver doesnt allow me to install with the existing image that I downloaded earlier. It downloads ubuntu afresh prior to installing. Is there a way to install it with the existing CD image and WITHOUT use of an external CD/DVD (too lazy to buy one :P) I used to be able to do this with the earlier versions of Ubuntu just by mounting the CD image as a drive in windows... and the installation would complete in minutes (HowTos)