Windows 7: Tablet PC Features
In the past, Microsoft required that you own a tablet PC and a special version of Windows in order to activate tablet functionality. However, it's now possible to access tablet features in Windows 7 on any system, so long as you license the Home Premium, Professional, Enterprise, or Ultimate edition.
The only bummer is that you need to upgrade to Windows 7 Ultimate if you want handwriting recognition support for a language other than English. The Asus Eee Slate ships with Home Premium.
Upgrading isn't cheap. You should expect to dish out another $100 for the Windows 7 Anytime Upgrade (Home Premium to Ultimate).