I just upgraded my old desktop to Windows 7, and so I've been poking at my hardware to see how it's performing with the new OS. When running CPU-Z I noticed my RAM (DDR, PC2700) is running at 164.4 Mhz. Theoretically it should be running at 166 Mhz, so where is that extra Mhz or so going?
More aboutdram frequency running approx
Nothing wrong, the memory controller does not always show the exact frequency you have.
I would suggest you to upgrade your computer though, as Win7 should not be that light on your system.