Tried vacuuming it out, helped a bit, but still it's running way too hot/fast/loud every time I am watching a video file or webcast. Any recommendations?

anyone?

Recommendation: Give us a little more info, makes helping you somehow easier.

I had to do a quick google to find out you're talking Notebook.

Since this seems to be a Notebook, only way is to open it up and remove the dust inside. If you do not feel like tearing apart and reassembling this thing by yourself, you should turn to HP support. In case of still having warranty, contacting HP support would be advice No. 1.

Compressed air is much more effective than a vacuum. Buy a can, open your laptop(removing the keyboard might suffice to get access to the cpu cooler) and use that.

But wedge something against the fan blades so it doesn't rotate when you blowing on it. The compressed air stream can cause the blades to rotate very rapidly which can be bad for the fan bearing.

Use an anti-static brush to effectively get rid of the caked on dust from both heatsink and fan. Worked great for cleaning my Dell XPS M1330. I just shoved the bristles into the heatsink, gave it a jiggle, and it came out looking like new. Compressed air will only remove loose material.