Here is what it says in the info on that Ebay link.
LGA775 socket for IntelR Core2 Dual/ Pentium D / Pentium 4 / Celeron D Processors
Compatible with Intel 05B/05A/06 processors
IntelR EM64T / EIST* / Hyper-Threading Technology ready
* Refer to www.asus.com
for Intel CPU support list
It doesn't say quad core. And here is a New egg link and it also doesn't say quad core support.
It supports the core2duo but not quad cores like the one you bought.
Edit: I see worshipme beat me, Damn dial up! And to CRYMAN DO NOT TELL PEOPLE THINGS WILL WORK WHEN YOU DON'T KNOW WHAT YOUR TALKING ABOUT!!!
If your not 100% it will work DON'T SAY IT WILL WORK.
And besides that you didn't save him anything since he already bought the board. Hopefully the seller will issue a refund. But looking at his terms I think the OP is SOL.