Partitioning my HD and external HD

The HD that came with my laptop is supposed to be 100gigs, but all I can access is just around 80gigs. And my external drive (which is supposed to be 350gigs) only has 290gigs.

I got partition magic, but, (to no ones surprise) couldn't do anything with it. My internal HD has about 7mb of unallocated space and my external HD has nothing unallocated. Does anyone know if theres a way of using partition magic to get the full 100/350 gigs out of my drives?

Though, I'd like to know other methods as well...my aim is to try and do this without having to format, but if thats impossible my stuff is already backed up

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also, a completely unrelated question; is there any way for me to add ram without taking my laptop apart?