Windows Vista Vista will not Boot

Greetings, my Vista Ultimate 64, is giving me problems.
A: at times it will shut down and reboot on its own, but will never reboot completely. Goes though process, winds up with a quick flash of blue screen and start over again, again. etc.
B: The only way I can get it to start, is to have it boot from the original DVD and go though the restore process and the takes up to much time.
It checks a bunch of stuff with error code=0x0, but at the end it tells me that "Root cause found unspecified changes to system configuration might have caused the problem" Once I get it booted up she works fine until the shut down and rebooting.
C: Also, some of the Windows update filed fail to install. I did install service pack 2 with no improvement to my problem.

Hope there is a solution to this, Please.
Thank you for the help.

 

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