|There is no "ddr2-5300". If you have DDR2-533, it's PC2-4200. If you meant PC2-5300, then you have DDR2-667. Either one will work but both are the "wrong" RAM. The A64 & A64 X2 are optimized for DDR2-800 aka PC2-6400.|
Before upgrading the CPU, do you have 4GB RAM & a PCIe video card? If not, those may be better places to invest your upgrade money.