I have this funny situation. Got a new Zotac G41 Value motherboard. Put in 1GB of 667MHz RAM and a Dual Core E2180 processor, 2.0GHz, 800MHz FSB with 1MB cache. Installed Windows 7 Ultimate. Ran fine. Then I upgraded to a E7500 processor, 2.93 GHz, 1066MHz FSB with 3MB cache. Still with 1GB of 667MHz RAM. No changes to the operating system in any way. What happened was that performance dropped drastically. Programs took ages to open although Windows startup was fine. It took quite long to shut down though and it was like running Windows 7 on a system that's like 5 to 6 years old. Worked but really slowly! Switching between programs was a nightmare too. So I got myself a 1 x 2GB piece of 800MHz RAM, took out the 667MHz one and lo behold! Everything was ok. I'm not much of a person for calculations but I've assembled quite a lot of systems over the past 10 years. This is the first time I've come across a situation where a piece of RAM can make such a HUGE difference.