JPEGSpinner is a little front-end application to jhead and jpegtran which will allow you to quickly perform several lossless transformations on JPEG images. It will allow you to rotate to multiples of 90 degrees, flip horizontally or vertically or automatically rotate based on information embedded in the image by the rotation sensor in your camera (if available). Since the transformation is lossless, there is no loss in quality due to recompressing the image.

To install: copy the application to your Program Files and create a shortcut in your Startup folder (sorry no installer yet).