Help me Please with my Dell Inspiron n5010

Hello my name is Anton Zhilnikov . I write from Greece.
I have Dell Laptop Inspiron 15R , Service Tag : <Admin Note: removed per privacy policy~RK>
From Octomber it have problems like Skype dont work or work for 1-3 minutes then just say "program Skype stop working" didn't run any game that i was running before the problem , freezes when i play youtube or try to watch videos in internet , Internet Explorer , Firefox or Google Chrome didnt work properly often freezes, and PC need restart to start work again.
I have communicate with Dell support here in Greece. First time i send it to them, they try to fix it by doind format but it didnt help. All those errors continue to exist. Second time i send it, they try to fix it and said that they change motherbord but when it come home i open in and all errors still exist . I call them third time, one guy from technical support connected to laptop with support session program , did format and install all drivers. But it didnt fix it same problem. The guy from thechnical support agree to get it again in Dell office here in Greece and fix it. After one week it come back , laptop didn't have problem with videos and youtube, but Skype and games still didnt work. Fourth time i call them they just say dont use Skype use another program and dont install any games. That was they last answer before my warraty endet. My laptop had warrantyuntil March 2013. What else i can do , because i dont see help from Greece support . Please help because this kind of behavior is unaccessible.
I ask you to help solve this problem please !
Sorry for my English . Thanks.

Best Regards
Anton