I should mention that these threads in the discussion forum are auto-generated when creating an article - I just added a little one for people searching for the min requirements of W7 Once time goes by and we get something more concrete, I'll add some more detail to it.
Over Easter weekend I only had my laptop with me, and I was also surprised to find how well Windows 7 performs on a low spec machine. After some tweaking the speedstep settings in the BIOS, I got the Intel Centrino CPU to run at 600Mhz, rather than 1.3GHz (with the full 512MB ram the laptop has). It ran okay... about the same as XP on the other partition. I would actually consider putting Windows 7 on the laptop as the primary OS once it is fully released.
After searching the net, I found someone running Windows 7 at 500Mhz. I'd be interested to know if it has run on anything slower