Vista Service Pack Install Problem

I tried downloading the Service Pack for Vista on my computer last night. It was about to finish step 1 when it said that the service pack did not install and reverting changes. It then preceded to shut down. I have been getting the same message all night! All the answers I have found online the people were able to get to their start menu but I can't even get to that because every time it restarts it tells me service pack did not install and it tells me it is shutting down! WHAT DO I DO? PLEASE HELP!!!
Jason

What SP? SP1 or SP2 Beta?What error code this error return?

Try
1.Standart methods http://www.vistax64.com/software-tools/183498-windows-update-reset-repair-tools.html
2.Description of the System Update Readiness Tool for Windows Vista and for Windows Server 2008

I'm not sure it is the latest one i guess. It searched for updates last night and said I needed to install it i think it was service pack 1. It is not giving me a error code it just says service pack did not install. reverting changes. do not turn off your computer. It wont even let me go far enough to get to my password screen to get into my start menu.

Boot DVD Vista

Choose language >>Repair computer>>System Restore

and restore system to any previous point.Next boot your system and try methods what I gave you in post2 and again install SP