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Can I use the installer to install Ubuntu and then go and delete Windows Vista while I'm running Ubuntu?
The Windows Installer (WUBI) avoids partitioning the hard drive by creating a virtual partition as a big file inside the Windows partition. It also allows uninstalling Ubuntu in the same way one would uninstall a Windows application.
An WUBI install of Ubuntu depends on components of Windows for (a) installation, (b) during booting to Ubuntu, (c) and for uninstallation.
So if you erase (or uninstall) Windows after installing Ubuntu using WUBI, then Ubuntu will not work.
Create a Live USB/DVD and boot from it. Instructions for burning an Ubuntu installation DVD are here: http://www.ubuntu.com/download/help/burn-a-dvd-on-windows.
Choose "Try Ubuntu" first and make sure everything (sounds, graphics, Internet) works.
Click on the Install button if you are satisfied. You will be given a choice to erase Windows.
Warning: This choice will erase all the existing partitions, C: D: etc. and all the data (songs, pictures, etc.). Make backup copies of all the valuable data in an external drive, DVD or some such things before trying to install Ubuntu.
Hope this helps