No need to upgrade ram just for speed ,PC26400 (=800Mhz ) rams can work on pm965 chipset because they are backward compatible and work at 667 MHz , no speed gain . If you are upgrading rams also you can buy DDR2-800Mhz =PC 6400 mhz i think price same and/or is not much different .
My advice ;get Get DDR2-800Mhz (PC' 6400) ram if price is same and/or close with 667( Pc2 5300 ) they will work on Pm965 at 667 MHz .Btw reguler Pc and notebook memory modules have different sizes (= you cant put a PC memory module to notebook )
http://ark.intel.com/products/29822/...ory-Controller you can see chipset supp orts DDR2-533 / DDR2-667