Hi gopudo, welcome to NST.
Ubuntu
isn't a program you run under Windows.
It's an
Operating System like Windows XP or Windows Vista.
If you installed it to your Vista Partition, it will have
completely overwritten the whole of your Vista OS.
(It will have given you a warning message when you clicked on Install, telling you that it will destroy all of the contents of the HDD if you proceed)
If you want to install an OS like XP or Ubuntu on your PC, you must first
create a new partition on the Vista HD from some of the unused space, or else install an extra new Hard Disk if you don't have sufficient space on your current disk.
What is the make of your PC ?
If you bought it with Vista pre-installed, it will have come with a hidden recovery partition, or else a set of recovery disks that will enable you to "factory reset" the PC back to the way it was when you first got it. I'm afraid that you will have lost all of your personal data which you created since that date, unless you have been backing it up to external storage.
Let me know the make and I'll help you find the recovery instructions.
These are the sites for
HP and
Sony