A convertable netbook may be what you a re looking for. Asus is apparently about to introduce two of them, there is also the
Gigabyte Touchnote T1028M and Intel's
Classmate PC "tablet". Note that these are running Windows XP Home, not Windows XP Tablet PC Edition. Vista has more support for tablet stuff (i.e. it is already a "tablet edition), but requires a more powerful computer. Battery life is always something to watch out for.