Woffen - I'm sorry to hear about your situation, I'm always bummed when any of my hardware dies (whether its my fault or not). With that said I think your handling it the right way by being honest about what happened, DFI is one of those companies that takes the time to actually look over RMA'ed hardware before shipping out a replacement (unlike some larger companies that can afford to ship out replacements without fully testing and researching the RMA'ed hardware). I've owned multiple DFI motherboards and for the most part I've been very happy with them (fortunately I've never had to RMA any of them). I have heard from many people that DFI is not the easier company to get RMA service from, especially if you don't in the States or in Taiwan. With that all said I did some quick research and learned that DFI has a brand office in Europe (Netherlands), if you continue to get nowhere with the retailer you bought the board from maybe you could get some help by contacting the branch office below?
Diamond Flower Information(NL) B.V.
Shannonweg 11, 3197LG,
Rotterdam / Botlek, NL
TEL: +31(10)296-1840
FAX: +31(10)296-1849
If not I'd suggest trying to contact DFI direcly (if its even possible) and explain your situation. It seems clear from what you have posted that you didn't do anything wrong, as you mentioned DFI is known as an "Enthusiest" company so I'd be very surprised if they voided your warranty coverage for running stability testing software with overclocked settings? Your best bet however would be to get your local retailer to handle this, infact they should give you a replacement motherboard and deal with DFI on their own (at least I think that is the way they should handle it, it makes good business)! Good luck and please keep us posted about your experience.
DFI Inc.
100, Huan-Ho Street, Hsi-Chih City Taipei Hsien, Taiwan, R.O.C.
TEL: +886(2)2694-2986
FAX: +886(2)2694-3226
E-Mail: dficmbsales@dfi.com.tw