Cost in Euros
HDD 640GB = under 70
8800GT gfx card = ~130 (keep in mind that AMD 4850 outperforms it easily and costs just ~150) (also means you need PCI-E, otherwise you're stuck with your current card no matter what)
DD2 RAM 2gb kit... well, starts from ~50 and can go as high as 150+.
You got a semi-decent rig, esp if you have DDR2 and not DDR1. Also make sure if you want to keep your current RAM chip make sure that you dont buy ram with much better speed and timings since your system will use the slowest memory module speed available to operate.
Also a 8800/4850 will give you another year of gaming, but this may require a better PSU.
As for a new processor.. well this means you'll have to move to a different mobo as well (plus another reason to get a new psu) since they require a new socket.
Tbh, the best way yo go here is either keep this rig and wait till you can really spend some money on a new pc, or just get a new one without spending much. Right now phenom is a good platform, esp if you are not able to overclock, because, at least according to amd, it is a platform that guarantees upgradeability, unlike Intel who are releasing a new platform ~Q1 2009.
Now if i were you id go for a 4850 and give my self one deecent gaming year till I have enough to go for a completely new system