in cmd use...attrib -r c:/readonly.txt

"Unlike the Read-only attribute for a file, the Read-only attribute for a folder is typically ignored by Windows, Windows components and accessories, and other programs. For example, you can delete, rename, and change a folder with the Read-only attribute by using Windows Explorer. The Read-only and System attributes is only used by Windows Explorer to determine whether the folder is a special folder, such as a system folder that has its view customized by Windows (for example, My Documents, Favorites, Fonts, Downloaded Program Files), or a folder that you customized by using the Customize tab of the folder's Properties dialog box. As a result, Windows Explorer does not allow you to view or change the Read-only or System attributes of folders."


http://support.microsoft.com/default.aspx?scid=kb;EN-US;326549