add a video card for my dell n5050 laptop

Sorry, no.

I tested the capabilities of the Intel HD 3000 in my laptop (Lenovo IdeaPad Y470; nVidia GT 550m disabled). I found it capable of playing Mass Effect 3 @ 1366x768. I would say the average frame rate would be mid 20's. Still I was able to complete the game on insanity level.

I was also able to play Fallout 3 with a mix of low and medium graphics quality. The only real issue was getting it to run stable in Windows 7. You will need a D3D9.dll file originally created for Oblivion (the Oldblivion Project) which allows the game to recognize the Intel HD 3000. Naturally Oblivion should be playable. And I would suspect Fallout: New Vegas is playable.

I would say it's good enough for Skyrim as long as you have low expectations, drop the resolution to 1280x720, turn off shadows and grass. All graphic settings are to low except textures which remained at high. If textures were set below high with all other graphic options set to low as well, the graphics simply looked fugly.

Object and actor fade distance options were set to the maximum of 15 because I use the bow a lot and I like snipping my targets from very long distance. Most other settings were set to absolute minimum or pretty low.

I found Skyrim to be playable enough as long as I kept my expectations low. I tested and tweaked the game until I got to level 10. So I was play testing for quite some time.

Needless to say Skyrim plays and looks better when I enabled the GT 550m.