Well I'm guessing your in Spain, so just go to Kingstons website
Select Spain from the counrty list and were to buy from and they will give you a list of sellers.
Their also a part number list below and as you can see Kingston make 1GB DDR modules all the way upto DDR400.
Part Number List
If your intending to put more than one into a system keep them the same (2x1GB kinston modules) dont mix and match with other brands of memory or size. Alot of motherboards designed for standard PC's become awfully picky when dealing with such large amounts of memory.
Also you dont need ECC registered ram if this is just your personal workstation only servers or mission critical systems should use that stuff.