wich games are you going to play? And with a intel core 2 dou 2.8ghz you could probably OC it to around 3.6ghz if you got atleast 800mhz ram without doing any harm to it. And dont choose a nvidia card because you get less preformance for the price. I would recommend the Radeon HD 4650 1gb wich is a excellent card unless you have hopes for playing crysis on highest fro 500€, wich you wont.
I would also ask you why you dont want AMD? the amd 2 core processors are much cheaper but comes with the same preformance, if i were you, with the 500€ cap i would never get a intel processor. If you run vista you will need 4gb of ram with atleast 800mhz clock speed. If you run xp you will do with 2gb.
Take some cheap case no need for a uber chase that cools like a refridirator if you aint going to spend more money on your computer. But dont take the worst either!
For the rest of the parts i dont know so much about but i would guess you could make it with a 500W PSU and a pretty fair MOBO. When you take a MOBO take one with integriated sound card, the most have those but not all! Dont do the mistake i did with not checking that first
luckily i could trade it in and switch it for another.
But however if you would like to go just a little over 500€ i would take the Radeon HD 4870 1gb instead since it's quite much better, but quite much more expensive aswell.
As i said
Choose a AMD processor
A Radeon 4650 1gb GPU
And a decent MOBO
500W PSU
4gb 800mhz RAM (vista) 2gb 800 mhz (XP)
Fair chassi
500gb SATA harddrive
well, a fair dvd burner.
Here is links and a calculation:
CPU
http://www.komplett.ie/k/ki.aspx?sku=451987 have better OC then the intel i think. 3.4 shouldn't be a problem with that one.
GPU
http://www.komplett.ie/k/ki.aspx?sku=442781 a really good one for a low price
PSU
http://www.komplett.ie/k/ki.aspx?sku=337116 acutally 630W wich is great
MOBO
http://www.komplett.ie/k/ki.aspx?sku=480481 a great mobo with really sweet OC features
CASE
http://www.komplett.ie/k/ki.aspx?sku=323083 my current case and i love it
Memory (vista)
http://www.komplett.ie/k/ki.aspx?sku=338074 great ones
Memory (xp)
http://www.komplett.ie/k/ki.aspx?sku=344667 they are good aswell
HDD
http://www.komplett.ie/k/ki.aspx?sku=352541 the one i have, it's really good
Floppy drive
http://www.komplett.ie/k/ki.aspx?sku=343919 i guess it works
Well that pretty much covers it and the total cost of it is actually only 450€. So if you would like to go with a 4850 1gb GPU instead it would end at 520€ wich aint so much over your budget but still gives some better preformance. And if you have XP the cost would be 500,61 € with the 4850 wich i think you can handle
All this is extruding fract costs. And if you live in sweden i would really recommend buying all this stuff from komplett.se. They have better offers and they are really fast!
Hope my opinion helped.
But if you under no circumstances can take a AMD processor you can choose the one you already chosen. It will be a little bit more expensive and it will have the same preformance. NOTEICE, if you go with a intel processor you cant take the MOBO i've chosen for you!