Dell Inspiron won't reboot.

Hello,

About 2 months ago for some reason my laptop has been running amuck. A lot of my applications have cease to work. When I try to run them there's always a component missing. Even Firefox has stopped working for me. If I try to reinstall it, it stops working again after a few days.
I've tried to reboot it to factory settings but when I select "Repair your Computer" I get this blue screen and some errors. I don't know what to do now.
Is there another way to reboot my computer to factory settings without a CD?

I have Windows Vista, Dell Inspiron 1545.