ViSTA WILL NOT BOOT UP, NEED HELP!

Hello,

I would really appreciate any advice offered. I have a Dell XPS 410 desktop running Windows Vista. It won't boot up, goes through POST, then the Microsoft page with moving bar, and then immediately goes to "No signal" and monitor goes into sleep mode. I have tried running startup repair and it says it cannot repair. I have tried system restore which did not work until I restored all the way back 15 days and then it would boot up in safe mode but it will not let me run virus scan or uninstall. When I restarted it went right back to the black screen. When I push F8, then I can do the diagnostics to no avail, When I push F12, it goes into a Dell diagnostic service, and I have run all the tests in that symptom tree. I did not get any errors but still cannot boot it up. I have tried unplugging the printer and all USB devices to no avail. One more interesting observation, when I try to boot it up, the first page showing has white dots on a black background all over the screen instead of just a black screen, the second page with the Microsoft bar has a regular pattern of three vertical green stripes going up and down across the entire page and the next page is the totally black screen. Even when I was running the diagnostics in safe mode, my background screen was blue but I could still see the pattern of three vertical stripes in that background although they were not green as they appeared on the black background. Can anyone offer me some help to fix this problem?