Please give info of your mother board.
P.S. dont listen advices like: "go buy i7 or change platform this one is old!"
when i see advice like that, i know that knowledge of that person about hardware is 0..
you have old 775 socket...go on ebay and search for core 2 quad processor....depends on your motherboard FSB...can be 1066 or 1333. Those procesors can be found under 50$ on ebay and you have 10% less preformance than i7 in SL for 1/10th of price! Dont be naive and splash lot of money on new platform for getting 5 fps more...
3 things you need:
1. if your motherboard support 1333 fsb processors: go with q9300, q9400, q9550, q9650......all are great processors and will hadle SL without sweat!....if your mobo support overclocking (good chipset on mobo)....you can easy match all i5 configurations for 5x less price
2. Power supply.....go with brand quality, that have enaugh 12V rails and amps to support good Nvidia Graphic cards
3. Graphic card: this is most important part...go with Nvidia GTX models. i rec. GTX 660, GTX 560 ti, GTX 760....deppends how much money you have
4. SSD for operating system only (Hard drive for storage and SL chache)
5. optimise your system preformance, turn off everything you dont need...
with my configuration...similar like that...i can play ultra with 256 m draw distance and 10 avis......no less than 10 fps up to 30 fps..
DONT WASTE MONEY ON FANCY HARDWARE for SL......inform your self on internet....
my 400$ pc is so good optimise, is faster than any laptop on this world
amen