Macbook Upgrades

Just bought myself a macbook 13" beleive its an old model, not sure on all of it, but basically it was an amazing deal as its ex display, anyway, trying to work out how i can upgrade it, as i have the spare cash left over and would like to improve the performance as much as physically possible, but dont know the constraints.

Heres some info from my system profiler

modelname: macbook
modelidentifier: Macbook2,1
Processor name intelcore 2 duo
Processor speed 2GHz
Number of processors 1
Number of cores 2
L2 cache 4MB
Memory 1GB
Bus Speed 667MHz

Hope someone can help let me know anything i can upgrade and the most i get into this thing!! also whats the largest hard drive i can get

Thanks very much

p.s any key software advice.

For notebook HDD the highest right now is 500GB.

I recommend this one.

Currently it's the only on the market that runs at 7200 RPM.