Aright not sure if this has been said but let me just straighten out some facts.
If you get a new mobo it won't fit into the dell case
If you get a new case the dell mobo won't fit right for the motherboard.
Your normal motherboard has a form factor of whats called 'ATX' boards that are the biggest ATX is called 'Full-ATX' because there are tinier boards called Micro-ATX.
So just remember when someone says 'ATX Board' they are talking about the actual shape of the board.
The processor, graphics card, RAM, HD's will all work with a new motherboard, although you might have to check the actual specifications of the processor to match it up with an appropriate motherboard and since it's an Intel you'll have to get someone who knows Intels, because I honestly don't know crap about intel machines.
The only thing that's incompatible like we said is the fact that a new mobo won't fit in that case, and if you get a new case, that dell mobo won't fit right into the new one.