bottelnecking

Hello there, I have a PC with following specs: AMD ATHLON II X2 240 @2.8 ghz, Asus M2N68-AM PLUS Mobo, 1GB DDR2 800 MHz, Powercolor HD 5670 1GB, 80GB PATA HDD. The problem is that even Spiderman WOS and Crysis doesn't wish to crawl on my system. It plays sluggish even on lowest...