I have a compaq presario notebook that I have took apart to with a can of air. I have taken it apart about 6 times before to clean it and all went well but this time I took off the heat sink and fan so i could get at it better now I cant get the heatsink to set right on the cpu. When I turn the computer on it instantly overheats and shuts off. I read the manual and it said every time you change the cpu you have to change the thermal pad but I do not see one on there and dont really know what one is. I orderd a tube of artic silver and aplied that but that did not help either. a couple of times I pressed down on the heat sink as I powered up computer and it ran fine, now I cant even do that. When I look at the heatsink I can clearly see where the cpu core was touching and it was about 1/3 of it. any help will be great.