At first I didn't but and it ran alright, but I wanted to see if it would make a difference increasing its speed by 200mhz. It gave me a lil performance boost. Probably not worth it in the end, but it didn't hurt to try. I saw your guide btw, not bad. I notice that lots of people never turn on intel speed step. It really does help with longevity and power consumption. Someone has to pay the bills lol.
Anyways, what memtest? You mean the windows memtest?