Nvidia is serious about getting its ARM-based processors inside Windows 8 systems. The company is working with Microsoft to supply developers and device makers with Windows 8 systems based the Tegra 3 SoC. It's unclear whether the "test PCs" are notebooks, tablets, or stripped-down development platforms like the Tegra 2-based Trim-Slice desktop released last year. Given Win8's focus on touch, I wouldn't be surprised touchscreen displays were involved.
The Tegra 3 is already out in the wild, of course, most notably in the Asus Transformer Prime.
Nvidia also has an interest in getting developers more familiar with coding for the ARM architecture in general. At the Consumer Electronics Show last year, Nvidia revealed Project Denver, a plan to produce ARM-compatible CPUs for desktops and servers. We haven't heard much about the initiative since, but if Nvidia intends to compete with the likes of AMD and Intel, it's going to need applications that run on its CPUs—and systems built around them.