Accidental wrong order, what to do?

[AxelCaedus]

I recently came to these forums and asked about buying parts for a cheap PC, and was answered by a couple of users pretty soon with a solution. I was looking for a PC around $300 with no monitor, keyboard or mouse. One guy gave me this build:


CPU + MOBO
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.543262

HDD
http://www.newegg.com/Product/Product.aspx?Item=N82E16822152244

RAM
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231277

CASE
http://www.newegg.com/Product/Product.aspx?Item=N82E16811119205

CPU HEATSINK
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103065

TOTAL: 302$

Perfect for my needs, cheap yet relatively powerful. Everything seemed to check out, everything was compatible, so I placed the order a few hours ago. Just now I was looking over the pictures of the motherboard, and to my horror realized it only supported DDR2 memory, and I had gotten DDR3 memory.

So, my question is, what's the cheapest way to remedy this. Should I change the memory, or the motherboard? Considering that the motherboard had a combo discount, I'm leaning towards the memory. Help?

 

[mianmars]

which CPU is it? combo link is no more active.