is motherboard 915 compatible with DDR2 ram?

Answer 1

Actually 915 chipset supports both ddr and ddr2 RAM. So it really depends on how the motherboard maker physically implements it. Samples:
1. Both ddr and ddr2
http://www.asus.com/products.aspx?l1=3&l2=11&l3=25&l4=0&model=164&modelmenu=1
2. DDR ONLY
http://www.asus.com/products.aspx?l1=3&l2=11&l3=24&l4=0&model=632&modelmenu=1
3. DDR2 ONLY
http://www.asus.com/products.aspx?l1=3&l2=11&l3=24&l4=0&model=540&modelmenu=1

Answer 2

Yes but only 533MHz.
It does not support 667MHz,800MHz and 1066MHz.


http://www.intel.com/products/chipsets/915g/index.htm