Weird screen when using Ubuntu Linux 8.04?

I’m trying to install Ubuntu Linux 8.04 on one of my computers at home. Now, I want to do this because of one particular reason: Windows Vista Home Basic has to be the Worst OS I’ve ever user in my entire life. Don’t get me wrong. I like Microsoft, but let’s just admit that Vista was a complete mistake that should have never happened (especially with Home Basic, which is useless and has nothing that the actual Vista has to offer). Anyways, when I boot the computer with the Live CD I made, Ubuntu starts up and operates everything normally, but I see this constant wierd pattern of smushed up lines that are displayed like a grid. Not only that, but a 1/3 portion of the screen on the right appears on the left, and I have to move my mouse all the way to the right to make it to that portion of the screen. Now, I don’t believe it is the CD. I’ve tested it on my other computers, and they work fine without this problem. This problem doesn’t exist when I run Vista either. What is wrong?
The computer is almost brand new since I never use it. Windows Vista Home Basic. It’s 80GB hard drive has nothing saved on it at all except the Windows system files. The CD worked while I was using Vista, and the drive is capable of the CD-RW I am using. I had in mind that it might be the moniter, or the processor, or even the graphics card. But all of those work fine when using Vista.