Hi newcomer and welcome to the Tom's hardware forum.
@mosox: Sorry u are wrong.
Here are two mobos that support DDR2 and DDR3
2- ASUS P5G41C-M
Exist much more but remember that u can't use DDR2 and DDR3 at the same time.
Now if u ask if u can use DDR2 in DDR3 slot, no it's not possible.