I have both 2003 and 2007, and I can't set it to exactly 14.25 in either system.

As I eluded to earlier, doing so would require Excel (and the operating system) to be able to use just a partial pixel to display the column width, which I'm not sure is even possible. The column can be either 104 pixes (14.14 characters) or 105 pixels (14.29 characters). There is no pixel between 104 and 105.

If someone can prove otherwise, please, feel free!