Looking at MSi Afterburner right now, its running at 87C with only 2 tabs of Google Chrome open, and WoW running in the background on low settings. As well, the GPU Usage is at 8%. Something seems amiss.
That kind of temperature isn't caused by dust. A few questions. How long have you had the card; did you receive it in this condition or has it just started to heat like that?
Make sure that the fan on the card is operating at all times. Sometimes a catalyst update will cause strange things to happen like fan problems and the such. If it isn't you may try setting it to manual fan control in the catalyst control center.
If that did not help give me some more information before I continue.
I built the computer back in September of 2010. The card came in perfect condition and I havent had any problems with it until about 3 months ago. I can hear the fan working. I set the fan to 100 percent just in case when i get on something like WoW or LoL. When I'm not running a game of some sort, it idles around 50C or so.
Is your card still under warranty? If so that is the route I would suggest. Otherwise it could be something with the heat sink / thermal paste. If it were a more expensive card I would recommend replacing that but seeing as you can buy a new card for that much it would be a better route aside from using the card warranty.