I don't know if you do your own work but by now you've used CANNED AIR on the vents. The next steps are to reload the factory OS, retest and see if it's OK. If not we open it up to replace all the old heat sink compound. And you bet we clean as we go.
I run an hp pavilion dm4t-1200 with 4 GB ram and a Radeon HD 6370 with switchable graphics. My processor is a Core i5 (quad core i believe?) Ive made sure my laptop is plugged in, and switchable graphics are set to use the hi performance card.
I bought this laptop about 2 years ago, and put some extra money into upgrades that would keep it relevant for a while.
Despite this, I'm having some major issues with video playback. While streaming on netflix, the video gets choppy and out of sync with audio after about 2 minutes. Same with HBO GO. I used to be able to run video games like starcraft 2, arkham asylum, minecraft, and arkham city without any issues, as these game requirements are well below what my laptop specs claim to be. However, within the past month or so these games run choppy, and the audio is out of sync due to video slowness.
I did try playing videos from my hard drive through vlc and wmp and they worked fine. Additionally, my wii and ipad all stream netflix perfectly, so I'm doubting it's a connection issue.
The only hardware issue I've had recently is a cooling fan malfunction. It makes an awful rattling sound if I tilt my laptop and the fan stopped working for a period of a day or so. It does run now (with the rattling while tilted) and my laptop never feels overheated. Could this possibly contribute?