For checking temperatures use HWMonitor:
http://www.cpuid.com[...]
This is your RAM:
http://www.computersalg.dk[...]
But any 800MHz 5-5-5-18 DDR2 will be fine, however the price isn`t that big - so i would buy new one anyway.
You must remember that you have only 2 slots for RAM.
Your windows is 32bit or 64bit? With 32bit you can use only 3,25GB RAM - but you should buy those 1 x 2GB anyway.
I hope your "stromforsyning" is a good one ... graphic card - GTX 560Ti should be fine:
http://www.komplett.dk[...]
I don`t know if you are familiar with overclocking? Your CPU is 8 x 333MHz = 2,66GHz. If you set FSB from 333MHz -> 400MHz then you will have 3,2GHz cpu. But for OC a little knowledge + decent cpu cooler is needed.
If you don`t know how to OC - 2GB more RAM and new graphic card will make a big difference anyway.
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Antec P182 + NF-S12B FLX @ 400rpm, E6850 + NH-D14 @ 400rpm, 4GB DDR2 800MHz CL4, HD 5870 Vapor-X, Corsair AX850
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