Mur@t, it seems to me that you got your PC from Dell!?! If this is true then you should be dealing directly with them.
I do feel sorry for you if this is true because the only people that buy from Dell usually know absolutely NOTHING about computer hardware and rely on Dell support to solve all their problems.
Building a PC is very simple and even an old dogg like me knows how; I've built every PC i've owned since my first 486.
So MR. Dell-owner, i suggest you use what support you can from your PC manufacturer or get an adult to help you. Dell will probably void any contract you have if you open up the case on your own, tho, so be aware of any policy and procedure warranty proclamations they impose.
good luck
Ron_Dogg