My inspiron mini 1012 notebook will not STREAM MOVIES OR PLAY VIDEOS!! HELP!!

I have had my notebook since october of last year. I do not have a warrenty and the guy i brought it from was no help in solving my problem. Everytime i log onto youtube or any other website to stream movies or videos i get great sound quality but the video is very choppy and i dont know how to fix this problem. It was working fine when i first got it but after a few weeks i was unable to view any movies or videos on the go. I dont understant because i can create a movie and play it back fine but when it comes to watching a movie online it will not let me. i have wifi internet access and i usually connect to my mobile hotspot or a signal in my neighborhood. I do not have internet access in my home. I have tried everything. I even took the laptop to my friend's house where there is internet access available in the home through a provider and it still didnt work. I am clueless. I have rebooted the laptop and even restated it to the default settings to when i first got it and that didnt work either. so can someone please help me..I am computer illiterate. This is my first laptop...PLEASE HELP! THANKS.