Evan is incorrect about it not being in the OS.
I have two PCs in my office. One has Win7. In the Screen Resoluion dialog, you can change the orientation between the following values: Landscape, Portrait, Landscape (Flipped), Portrait (Flipped).
On my other box, I could do the same when Win7 was installed. But now that Server 2008 R2 is on it (same PC/video card), that orientation option is not there any longer. Wish it was, because this PC's monitor is a non-wide-screen 22" that can flip clockwise.
Any suggestions of a fix. I turned on the Windows Experience feature, but the orientation option still doesn't show.