Step 4: Elephants never forget because they have more than 1GB RAM
I popped in 4GB (two 2GB modules) of PC2 6400. Now, a word of warning. Windows-based 32 bit operating systems will only be able to see and use about 3GB, even if you have 4GB installed. Also, the Intel GMA965 chipset we've got will only be able to run the memory at 667Mhz max. So why did I get 800Mhz? Well, a couple reasons- it's just as cheap (if not cheaper) than the slower stuff; if I ever upgrade to a new laptop and use this one for parts, the parts are better; the 667Mhz timing on these modules is a bit tighter than the actual 667 ones... and last but not least, why not? To use a car analogy, I'd trust a sports car to do 80mph more than I would a Yugo, even if both are capable :) I don't mind a better margin of error without extra cost.
Also, do yourself a favor and buy memory off NewEgg or someplace reputable. You're shooting yourself in the foot if you save $2 by getting off-brand maybe-not-so-backwards-compatible modules off eBay from China. Honestly. Plus it'll get to you a lot quicker.