Ram upgrade for Toshiba Qosmio G20

[garry]

Hi just wondering if I could get some advice about upgrading the ram on a Toshiba Qosmio G20 laptop,I have never really tried to upgrade a laptop before,so I am not really sure what the go is with the ram.

The laptop is the Toshiba Qosmio G20 (model number PQG2OA-1OQ002
These are most of the specs
cpu pentium M780 2.26ghz
ram 1gb ddr2 PC2-4300 266mhz (2x 512mb sticks,going by what cpuz says)
harddrives 2x 100gb

I am not sure what ram to buy from pccasegear,this is the page I am looking at http://www.pccasegear.com/index.php?...&cPath=186_366
I am thinking about getting the 4gb kit at the bottom of the page,but I am not sure if the laptop would be able to run the 2gb sticks or not,and also I notice that the 4gb kit is rated at PC-6400,but the stuff in the laptop in rated at PC2-4300.

Does anyone have an idea about what kit I should be looking at,1gb just doesn't seem to cut it with windows xp,and especially vista,if I upgraded to 2gb that would be a desent upgrade,but 4gb would be even better if it's possible to run that much in this laptop.