http://www.winsupersite.com/win7/win7_rc_04.asp
"[My Previous Review] was inspired by my decision to test the Windows 7 Beta on a two year old Ultra Mobile PC (UMPC), which I felt would roughly emulate the performance one might see on a typical netbook computer. (I didn't yet have a netbook for testing.) My experience, however, was poor. "I haven't watched Windows redraw the screen this slowly since the time I tried to install Windows 3 on my wife’s 14 MHz IBM PC back in the early 1990s," I wrote."
"This UMPC has an 800 MHz Celeron processor and just 1 GB of RAM. It will not accept any USB memory keys for ReadyBoost purposes, so there's no way to even improve the memory situation. But it doesn't matter: Windows 7 just runs and runs and runs. It runs well enough to play a full resolution H.264 DVD rip in Windows Media Player (windowed or full-screen) without a hitch. In fact, I brought the thing to the gym Friday and watched 30 minutes of that movie while doing some cardio. Perfect."