Vista Tutorial - Blue Screen Error after install

I'll keep it short, Windows Defender is the problem on my machine it come
inbuilt in Vista and I don;t know how to disable or delete it so i have these
blue screen pop ups and the comp restarts every few minutes or hours. i had
to roll back to xp and then i installed defender again and again the blue
screen popped up, no i have uninstalled defender and so far it looks good. so
my guess is defender is the problem. if anybody knows how to uninstall it or
disable it permanently that would be helpful.