DDR2 1066 with AMD 5000+ AM2

[The Russ Bus]

So I built this new AMD rig, my first AMD build. Has an AMD Athlon 64 X2 5000+ Brisbane 2.6GHz Socket AM2 65W. Mobo is a GIGABYTE GA-MA78GM-S2H.
Anyhoo, the mobo supports the 1066 DDR2 RAM. I just learned that the those older, non Phenom, AMD chips dont support the 1066 RAM. WTF? Anyhow. The board boots up and its reads the memory as DDR2 800. Boots windows in safe mode (another issue) and reads it as 1.75 gigs from the System tab.
My questions are this. Am I going to have any problems with this 1066 being in there? Its aparently just running at a lower speed?
Next question is, if I get the DDR2 800 RAM and tick it in there, is it going to work fine? Backwards compatible yes?

 

[StrangleHold]

With AMD the memory controller is on the processor not the northbridge. The Athlons memory controller only supports up to DDR2 800. It should just back clock the memory to 800. If theres any problems you might have to set the voltage and timming manually in the bios. My board when I swaped it out, I really have DDR2 1066 but it just runs at 800. If you decide to overclock it will give you some head room plus if you upgrade to a Phenom later it will run at 1066.