which RAM setup is better and why?  i dont know what to do.  either buy 2 more gigs or RAM or just buy a new set of 2x2. 

I personally prefer 2 x 2GB sticks... even though I have 4 x 1GB sticks (price was too much)... From all of the reviews and articles i've read over the last few years, apparently, your RAM has the potential to perform better with 2 sticks compared to 4 (with total memory being the same). Plus, these days (for DDR2), you can get some pretty nice deals for 2 x 2GB on clubit and newegg.

Also, a friend of mine ordered what he thought was 2 identical packages of 2 x 1GB of ram... he set up all 4 x 1GB sticks in his comp and he ran into issue after issue after issue (crashing, etc.)... he ultimately found out that the first set he ordered were slightly different then the second set... despite the fact he ordered "Quantity 2" of the same item from Newegg... its a headache you could ignore by going for 2 x 2GB.

I hope your using a 64-bit OS :)

 2x2.

It is easier on the memory controller, and is better for expandability.

Any sort of frequency or latency benefits you might get from 4x1 would either be neglidgable, or actually worse due to the amount of voltage you would have to crank through your NB coupled with the increasing of timings, and or decreasing of frequency.

 2x2 will increase the memory transfer and it will be more benefitial however a single stick will just have its lonesome bandwidth therefore not being able to gain an increase in memory transfers