Slow Response Times When Opening/closing Apps And Programs

I need some assistance. I have a Dell Inspiron Laptop that runs Vista Home Edition. Whenver I boot up and try to open a program or application, it takes a really REALLY long time for it to open. For example, whenever I try to open Firefox or Internet Explorer or even my control panel, the window will open and will be blank. Then it will start to load but either take an enormous amount of time or, after I've become tired of waiting, I'll try to exit and it will say (Not Responding). Now eventually this goes away and the window does close, but like I said, it takes a ton of time trying to open and close these things up. If I do wait it out and I do get into my Internet Explorer or Mozilla, any links that I click or addresses that I type, it again, takes forever. I've run a deep system scan with my Anti-Virus software and came up with nothing. I did a system restore to a point where the problem was not happening and, again, nothing.