As one other well informed person replied, open PS (CS3), choose File> Browse> Open in Camera Raw. Only Photoshop CS3 and the very latest version of PS Elements has this capability; nothing else allows you to effectively change to the color temperature (white point) in a JPEG or TIFF after the fact; it is very easy and works just like the normal camera raw dialog when opening a standard camera raw file. All of the other methods that others have suggested will shift more colors than you want; fix your white point first and you likely not need to do any further color balance adjustments most of the time.
Regards,
Mike