Black screen on install CD, among other things...

Hi, I have a Dell Dimension 2400 Desktop Computer. It has 768 MB of RAM and an Intel Graphics card. I have been trying for a few days now to install Ubuntu 7.04 (Can't remember the name...). I put the CD in and the install screen comes up with options. Now, no matter which option I pick (ie: Safe Install, Disc Check...) It loads a gray box with green bars/dots. When those go away it comes up with a black screen with words about loading or something, then goes black indefinitely. I don't think it is a graphics problem but it is not ruled out. What baffles is me is that I have run the live CD of 6.10 before and it worked just fine. When 7.04 didn't work I tried the 6.10 and it did the same black screen problem. The only hardware changes I can think of is adding a hard drive. It currently doesn't work but is still in my computer. I have tried the alternate install Cd, and about 3 other mirrors of the ISO besides the actual Ubuntu.com dowload. I have tried burning the image with different programs in hope that it was just a burn error, no luck. While waiting for a reply to this I am going to try the minimal install while my cable modem is plugged in. Hopefully that will work. Also, If I do get the live CD even up and running... is it possible to install and boot on an external USB Hardrive? Osrry if it's off topic but just wondering. Thanks in advance for any help.

Stephen