Question: are all ddr2 ram compatible?
Answer: No, there are different types of DDR2 modules. DDR2 is more thought of as a specification. There are desktop and laptop modules as well as different speeds such as PC2-3200, 4200, 5300, 6400 and 8500. The modules are keyed different than DDR and DDR3 slots, so they are not backward compatible either.