I'm about to install Ubuntu by using Wubi. Can I then delete Windows and keep Ubuntu?
You cannot remove Windows after a WUBI installation. WUBI installs as a folder INSIDE Windows so if you delete your Windows partition, you will delete your Wubi-Ubuntu as well.
If you want to remove Windows you have 2 options.
Install Ubuntu as a dual boot and then after you know everything works you can remove your Windows.
Install Ubuntu and during installation select the option that will install Ubuntu on the entire disk. This will reformat the entire disk and wipe Windows in the process.
If you are sure that Ubuntu will work with your system then I would recommend the second one as it is less work, just make sure to save all your important files first.
If you are not sure if Ubuntu is for you, install as a Wubi system and try it, if it works on your computer and you want to wipe Windows you can either migrate your Wubi install or just do a Standard install (if you don't do alot of changes to your Wubi install, I would just do a clean install rather than migrate).
To remove windows and install ubuntu, you need to do the following:
Enter the BIOS setup(when the computer turns on, press del key)
Change the boot sequence so that CD/DVD is you primary boot device.(Every BIOS is different, look inside advanced bios settings if your machine is old and you are unable to find it)
Save and exit
When the computer restarts, Ubuntu setup should start
Select REPLACE WINDOWS WITH UBUNTU(on everything else click next, and I recommend to select install updates and install third-party software)
You can customize the installation, but these are the recommended settings