if you know how to code and and have the sdk here:
http://www.codeproject.com/KB/mobile...?display=Print
also google:
ppc upside down portait
there are a few apps out there, but be carful. they say they replace critical files on your device and it might not work. so you could be looking at a hard reset. best to try it on an extra device.
this is one:
http://www.nyditot.com/NVDPage.asp