Hi, I am a Linux user. Wubi is just for trying out Ubuntu. You can't get rid of Windows this way.
After burning a successful disc image with no errors on it Run Ubuntu in live cd. I am assuming u already tried it, liked it, and Linux ran well on ur hardware. When u start Ubuntu installation then get rid of all partitions. Now Windows will no longer be on ur hard disk.
Partitioning ur hard disk is a bit tricky in Linux. Assume u have a 100gb hard disk.
1.The first partition is called the root partition. It has a mount point of "/" and uses the ext3 file system. Make this partition of 20gb maximum. This is where Linux and all its updates will be installed.
2.The second partition will be ur home partition with a mount point of "/home" and uses the ext3 file system. This partition can be made of 78 gb. This is ur home partition where u keep all ur stuff like music etc and some of ur programs will be installed here.
3.Now 2gb is left, make this a swap partition with the mount point "swap". This is like extra ram and 2gb is what most people keep. This partition is also there for ur power management options like suspend to disk in Linux which is hibernate in Windows and deep sleep in OS X.
The rest of the installation is pretty simple. If u have any questions u may ask me or some one on yahoo answers or u can visit http://www.ubuntuforums.org
I hope I helped, welcome to Linux.
Good Luck and take care!