Alienware 17 problems! Games! Graphics! Help!

Hi,

Bear with me because I'm not great with computers and I'll probably do a horrible job of explaining this.

Earlier this week I started having problems running games that were until recently running perfectly well. Most of them aren't getting past the loading screens and if they are the frame rate is so choppy that they're unplayable, or I'm getting other graphics issues. I tried temporarily changing the video quality presets to lower settings and it helped a little bit, but not very much. Now when the games try to detect my video hardware and set the video options accordingly, they're all being set to Low or Medium at best, whereas a month or so before they'd be set as High or Ultra.

Overall the laptop has been running much slower than usual recently, it's been reaching a high temperature quite quickly and the fans start blaring as soon as I switch it on.