Ddr2?

Is there DDR2 that is twice as fast as ddr?

There is only one speed for ddr2 right now. .it is ddr533 or ddr4200 anything above that is just overclocked ddr533.

Well, DDR2 actually starts off at 400, then it begins to climb up to 533. It's not yet twice as fast, but it's still quite the increase, I'd say. (DDR2 @ 400 isn't well-known, kinda like DDR233....)