Vista Starup Problem

Hi, new here, and didn't know where to put this, but here goes (sorr
long)

I dl'd Mozilla Firefox a day ago, and everything dl'd correctly an
completely. But, when I shut down the cpu, it wouldn't start up at all

I did every diagnostic i could let the cpu do, ran a system restor
(went all the way back to 10/25/09 restore point). then, i got it to ru
in safe mode. played with start-up options, and got the desktop to com
up in normal mode, but then got error msg 0x800106ba (windows defende
won't load), this meant that none of my security stuff loaded either.
ran a chkdisc thing too, and it stopped when looking through file dat
(stopped at 16%)

thus, i am running the cpu in safe mode with networking, and the cpu i
running fine.

i know this means that there is a file issue. but i am not sure how t
find it.

please help

thank

--
mestan07