RAM Upgrade- Brand/Model Question

Hi. Im thinking about buying this Corsair 2 gb kit... http://www.newegg.com/Product/Produc...82E16820145486 for my Gateway 560GE (i know, i got it before i knew anything about the pros of building your own) but anyway, my computer currently has the 2 256 mb modules that came with the system and i added 2 non brand name 512 MB modules. I was thinking of replacing the 256 mb modules with the 2 1 gig modules. I hear that Win XP 32 bit can only utilize 2.75 gigs or something like that of the RAM. Will having 3 gb total in RAM have any negative effects on my system because it doesnt use it all?

The current RAM in my system is...

non-ECC unbuffered PC3200 (200 mhz) 64 bit DDR SDRAM running dual channel.

Also, does anyone use a Corsair kit like this. How is it? Thanks

O and one more thing.. What is this heat spreader stuff and what are the pros of having it?

Well you don't really need more than 2GB of RAM but there shouldn't be many bad effects as the corsair RAM is already timed somewhat slow (3-3-3-8). A heatspreader is exactly what it says, it spreads heat It's just that metal peice that is on the RAM chips.