Memory upgrade questions

Sorry if this is way too basic. I have a HP a1012x with 512 MB PC3200 DDR SDRAM but the system says I have only 384 installed...Anyway can I use DDR2 Ram with the already installed? Or would there be some kind of conflict? I saw a Gig of DDR2 on sale for 24.99 (after rebate) and was wondering if I could install it no prblems or should I remove the original memory first?? Second question is what is the PC3200? If I mix it with SDRAM PC4200 would there be problems? Any help would be greatly appreciated.
Kelvin

 

Firstly, DDR and DDR2 are a different "shape" of module and will not fit.

Also be aware that Laptops usually use the "SODIMM" format of RAM modules, so the more common desktop RAM "DIMM" modules will not fit.

Your laptop is probably using 128 MB of the installed 512 MB as video memory. Leaving 384 MB.

You need to check if the installed memory is 1 x 512 MB module or 2 x 256 MB modules. There will usually be only 2 slots, if they are already both used (2 x 256) then you have to throw one away. If it's only one module you can add another.

The 3200 is the "speed", generally faster RAM works OK, but there can sometimes be conflicts in rare cases.