Windows Vista and Windows Defender?

Okay, I'm getting real sick of Vista real fast! I'm seriously getting an Mac next time to avoid this crap. Anyways, I can't figure out a way to uninstall Windows Defender. It came standard on my Vista and it somehow managed to corrupt the harddrive and all this weird stuff that's been happening to my computer is because of Defender. It won't show up on the programs and features list even after I try to delete the shortcut and click on the link that would lead me to Programs and Features to presumably remove it. Anyone know how to get this off of my computer?