What is the difference between PC2-4200 and PC2-4300? They are both DDR2, and they are both 533MHz. Whats the difference? Also, while I'm starting a topic, if my Dell 4700 series accepts DDR2 up to 533MHz, un-buffered, non ECC, 240 pin, blah blah... is their any reason why non-dell brand RAM of those specifications would not be compatible in my Dell?
4200 is the standard. All ddr2 240 pin ram sticks will fit in that Dell board.
Good to know. The RAM I am buying is PC2 4300 though. Is that still compatible?
Worry about frequency, not PC-rating. All that denotes the the specification's maximum bandwidth for whatever speed, in MB/s. DDR3-533 is DDR2-533, regardless of whether or not it's branded as PC2-4200 or PC2-4300. I suspect that "4300" is more a marketing thing than an actual specification thing (by that same hand, I don't know that JEDEC has even ratified any DDR2 standards yet, or if they ever will). In any event, on a normal board either will work. However, as with motherboards and power supplies, Dell has a history of--you guessed it--using proprietary memory pin configurations. If this is the case on this board (and it may not be; I don't know if Dell is still doing this or not), then you won't be able to use RAM not designed for Dell mobos. I'd make sure that the vendor you're buying from will take returns on opened product.