There's that WinPortrait Pivot software which has been around a long time, but it doesn't work nearly as well as the NVRotate feature in the newer Detonator drivers that works on all GF4 and later cards.
The problem with WinPortrait Pivot is it really sucks if you have multiple portrait displays and/or a CRT involved. It wants you to rotate all your pivoted displays the same direction. If not, it'll just reset them to the same direction each time you reboot. It also forces all your displays to 60 Hz (although you can override this with something like PowerStrip).