Most tablets coming out these days are based in a cellphone operating system such as Android, as they're designed to be used with a touchscreen. But not HP! If this video is real, it shows their upcoming Slate running Windows 7. And man, it looks awful.
There's really no reason to run Windows on a tablet. It's designed for a mouse and cursor; a lot of functionality comes from hovering over things and right clicking on things, two things you just can't do with a touchscreen. The whole thing feels unnatural, doesn't it?
Fortunately, since HP recently acquired Palm, they should release another version of the Slate running Palm's WebOS, which was excellent when running on the Pre. I don't know how many people would choose Windows over that.