Of two different laptops that I have, one has a 2GB PC2 5300 (667 MHz) RAM module. (The other has two 1GB PC2 5300 modules).
Can I install two identical 2 GB PC2 6400 (800 MHz) RAM modules in one of these laptops? Dell's specs are not clear regarding the 800MHz memory. (I know that two modules of 2GB each 667 MHz will work).
It would be nice but unfortunately not. additionally these systems are prone to failure at any time if they have the discrete graphics option due to an issue with the NVIDIA chip used with that upgrade, however thats a bit of luck of the draw as I have had one for years that has worked great.
Unfortunately the Dell replacement boards on that second one will continue to go out in my experience. The warranty replacements are refurbished parts that Dell sends out that supposedly do not have the NVIDIA GPU issue when in fact they actually do (source: My time working at Dell doing support for the business models). To be fair Dell was not the only system vendor affected by the issue but if you are interested you can read more about it here:
That is where it gets tricky as all parts you get for the D630 are going to be refurbished parts. When Dell transitioned from D series to E series on the latitude line they ceased manufacturing pretty much all D series parts. Since most of the warranties have run out or will soon they rely on warehouse stocked refurbished parts to fulfill their warranty obligations. You may unfortunately continue to have the problem at varying times until you replace the system either through warranty (which again wont happen unless a strict set of circumstances are met) or through purchase.
To exchange a system Dell requires a mimimum of 3 major parts dispatches for the same issue within if i remember correctly a 3 or 6 month period or if you have an accidental damage contract the system must be damaged beyond economical repair. However...some of the motherboards they send out for replacement or originally will never have an issue, my D630 for example has never so much as even had a hard drive replaced much less a motherboard. It's sort of a shot in the dark.
The warranty replacements are refurbished parts that Dell sends out that supposedly do not have the NVIDIA GPU issue when in fact they actually do... if you are interested you can read more about it here: