Any of you have one of this old ram not use want to sell?
PC2-5300 would be 667MHz. You can get the DDR2 2GB 800MHz from MSY for $27-28 and it would work fine. These are getting harder to find as everyone is now on DDR3 which is getting cheaper by the day.
Not sure if it compatible with "Lenovo AMD Athlon 64 X2 4000+"?
Pretty much all DDR2 is backward compatible. What makes you think that your computer needs to have "special RAM"?
as i'm not sure if motherboard can handle that extra MHz?
The speed is a limit, not a requirement.