I have a Lenovo R61.
Am planning to upgrade the RAM.
Which version of DDR2 (667 or 800) should I use?
CPU-Z screenshot: http://valid.canardpc.com/show_oc.php?id=1545560
The R61 doesn't require DDR2 PC6400 (800mhz)--it's run with PC5300 (667mhz). I'd go with whichever one you can get cheaper.