That PC simply sucks. I wouldn't touch it even with a long stick..
Processor - Only part I'd MAYBE buy..
Graphics Card - Total shit, get 5750, 5770, , 5830, 5850, 5870 / GTX 470 480
RAM: Atleast 4 Gb 800 MHz (if Vista/7) 2Gb is enough with XP.
PSU: -.-' It's enough, but I guess it'll last about a year.. Corsair cx400 is good and cheap
You'll get i5 750, P55 motherboard, 2gb-4Gb DDR3, HD 5750, cx400W PSU with ~500-600 euro.
-Kessu