Ah, les ordinateurs! Comme logiciel!
Hmm, sorry, that's my not very good French language skills coming out there. Dell has been selling desktops in France for quite some time now. So you'll be familiar with their policies and offerings then, I assume? Their practice of holding no stock, of building the computer as you order it, means that they don't have to have huge stocks of components and finished machines. That you buy it direct from them also reduces the price, as there are no retailers to take a cut.
But if you're in the market for a desktop at the moment there's one overpowering reason why you want to take a very good look at a Dell. Because you don't have to get Windows Vista with it. They'll still sell you a machine with XP on it, a vastly better operating system.
So, a better computer, at a better price, with the software you want rather than what you're forced to have. Couldn't get better, could it?