Stupid Username :
I can see the chip under it. I looked around on google and found out the pny geforce 8400gs doesnt have a heatsink. So I guess thats mine. Im only 15 so I got hardly any money to spare.
Well now you know for sure. My youngest boy is 15 so I know that money is a problem. You did good by reserching your card and found out that card just uses a fan to cool it.
If you are trying to play any of the top games of today like BF3 or even the games just before the new releases with that card you are going to have those issues. You could try this.
When you want to play the games open up the side of your case and put house of desk fan to it to blow the air at your card and CPU. That should help for now untill you can get a xmas gift or bday or some day gift.
Other than that there isn't to much more left to do if anything left with out costing money. I have seen my son not be able to do stuff when he was really counting on doing it. So I do feel for you.
I wish I could have done more for you. You know you have tried everything to fix the problem. The next thing is money to fix it. Good luck and I hope you can get it going sone how some way.