Quick memory question

Is it true that DDR and DDR2 modules are completely incompatible? I’m considering upgrading to a Core 2 Duo / PCIe system in the next couple of months, but I have 2 gigs DDR1 RAM with ECC and a speed of 800 MHz that shouldn’t be substantially slower than the DDR2 equivalent. I’d save a whole lot of money if I could reuse that memory…

They are completely incompatible. Different pin layouts and everything.

Argh. So I need new memory, and my usual online retailer doesn’t even carry DDR2 800 sticks with ECC at this point. This sucks mightily. I think I’ll wait a bit longer before upgrading…