Ram is cheap find out how much you can stuff onto your mobo go to
www.4allmemory.com and see what type of memory you need and them google that typeof ram for the best price.
Fedora Core 3 is great it's VERY BLEEDING EDGE so if you don't mind updating quite a bit and you really know your stuff in a linux pt of view, i would say do it!!
my systems
Notebook
pentium mobile 1.5 ghz
intel centrino wireless
256mb ram < -- - works fine, but i want more
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Desktop
intel pentium 4 1.8 ghz
512 mb ram
intel d845 glva mobo
fedora runs almost flawlessly on the PC