iRotate from EnTech in Taiwan

Fantastic discovery! A simple application that rotates the display of any XP/Vista computer, including light-weight netbooks, to tablet-style orientation. Combine this with a Targus 2.4 GHz wireless optical mouse, and you can view documents in portrait orientation and navigate around very intuitively. You can hold the netbook sideways, like an open book, with the keyboard on the left and the screen on the right. The smaller netbooks are very light-weight and can be held very comfortably in one hand while open in this sideways orientation, like an open pamphlet. But unlike a tablet PC, you still have use of a full size real keyboard with no obstruction of the view of the document. If needed, the wireless optical mouse can be used to navigate and click even if still in your coat pocket with your free hand; or, you can take the mouse out of your pocket and move it on a desk.

So far I have just tested this with XP. The default settings work great. You end -up with hotkeys CTRL-ALT-leftarrow for rotation and CTRL_ALT-uparrow to restore, and on the MSI netbook the three keys are located conveniently together on the bottom right side of the keyboard. You can also toggle from the DOS command line as follow:

c:\Program Files\iRotate>irotate.exe /rotate=90

which got me out of a jam. (At first I had combined this application with the MSI netbook toggle for an external monitor (FN-F3) and my netbook was stuck in portrait mode). The documentation says you can control multiple moniters by editing the irotate.ini file and you can also assign the hotkeys to alternatives.
Documentation: c:\Program Files\iRotate\irotate.htm
Forum: http://forums.entechtaiwan.com

The cost: FREE.