Get the absolute minimum you can and upgrade when you get it. If you order 2GB of ram they’ll send you two 1GB sticks which makes it worthless when you want to go with more. Most laptop makes will let you specify 1x2GB but you get POS sticks and mix-n-matching good with POS is never smart. Get 512MB or 1GB and upgrade to a pair of 2GB sticks. Get some with good timings (4-4-4-12 or lower) and pop them in when you first boot it up.
You’re going to upgrade to 64-bit eventually so might as well get 4GB now while you’re in the spending mood.