Bad lag while playing steam games and watching videos

I'm running windows 7 on a Dell N5010 laptop
It works fine while just browsing with chrome or using skype, but as soon as I try to watch a video on youtube it won't play smoothly unless I have it on a stupid-low quality (with nexflix too)
same with my games on steam (I only have two downloaded right now- TF2 and Skyrim) and both of them are super laggy, even with the graphics, ect all set to low.. Minecraft does the same thing.
It gets pretty annoying as you can imagine.

I've tried closing all my background programs while playing and deleting a bunch of stuff to give more space on my RAM but nothing really seems to make any difference.

Any advice..??

You're running Intel HD graphics that's built in to your laptop. wont do ya much good if you want to play games or watch movies. bare minimum internet browsing. If you want to play video games on a laptop, i recommend getting a new laptop that has dual video cards. one for highperformance (videogames/movies), one for power saving. Also, your i3 processor isnt helping much either.

Generally, laptops are meant to be upgraded every 3 years. I'd also recommend a desktop if you want to play video games. cheaper, more powerful