it is ddr2 and it's not registered memory.
ddr2 is more expensive now as it not the standard used much these days so you pay a price premium as it no longer produced in large quantities
Thanks, it's odd as I've found what looks to work on ebay but they say it is not recommended for desktops only servers. Why would this not work in a desktop? 1GB DDR2 PC4200 PC2-4200 533MHz ECC REG 128X72 240PIN SERVER RAM
What is the difference? It looks like a perfect fit but the seller says it only works in servers.