Question: Recently I downloaded ubuntu 13.04 (iso). Now after extracting the iso file and running wubi - it says downloading required files though I had already downloaded the iso file (794 MB). So what to do now?

Answer: 
wubi in 13.04 is not in a releasable state. You have to install Ubuntu 12.10 through wubi and then upgrade to 13.04. follow this [steps](http://schoudhury.com/blog/articles/install-ubuntu-13-04-with-ubuntu-wubi-installer/)
DO NOT extract ISO files. Instead mount it using ISO mounting program, and run Wubi. I suggest use Wubi only when you using Ubuntu [12.10](/questions/tagged/12.10 "show questions tagged '12.10'")

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If you mean installing it on its own partition, instead use [live-usb](/questions/tagged/live-usb "show questions tagged 'live-usb'") from [pendrive](/questions/tagged/pendrive "show questions tagged 'pendrive'") using [UUI (Universal USB Installer)](http://www.pendrivelinux.com/).