Jeez! Computers! They make your life simpler.. except when they confound you by not working properly. Well its pretty simple folks. If you want to buy a computer you should look in the Athens Sunday paper, any larger Greek Sunday paper with circulars. Within you will find advertisements by different chain stores all of whom compete with one another and offer many products. You don't even need to speak Greek as there are many pretty pictures to look at with prices for cash and prices for installment plans.
You can also visit the shops in the Exarhia section of Athens on Stournari Street (where I live). Stournari is hard by the University of Athens and near the National Archeology Museum with Omonia Sq the closest Metro stop. On it you'll find many stores selling lap tops, peripherals, monitors, flash memory, and other components. They've got it all and it pays to shop around too!
My favorite chain store is Plaisio because they have a service center right near by and sell guaranteed products (for one year usually). They have their own brand of computers too "Turbo-x" and you can mix and match hardware and they'll build it for you. You choose your chip for example; Intel or Celeron? How many MB? How much memory do you need? How about a nice Graphics card? And so on. I have bought three computers via Plaisio and generally like their style. Its a young business with young employees and a fairly (by Greek Standards) can do attitude. They even speak English usually.
Recently a new German chain, Merk Mart, has opened one location in Athens at the big new mall with all the recent fanfare and is supposed to the biggest electronics chain in Europe with really good prices. I haven't actually been yet because I am not in the market at the moment. To tell you the truth, I like the fact that if anything goes wrong with my computer I can carry it right down the street. Think about that before you buy the slightly cheaper computer as sooner or later it will develop a problem. Plaisio will also come to your office or home if need be. Dell recently opened in Greece but look a bit less consumer oriented just from glancing at their site.