If you use Visual Studio to edit your Wix projects (either using Votive or just the plain XML editor), you may be interested in this handy little shortcut key. If you turn on pedantic checking for your WiX files, one of the warnings will be about having mixed-case GUIDs. The easy fix is to select the GUID and then go to Edit / Advanced / Make Uppercase (Ctrl+Shift+U). Voila, your GUID is now all uppercase.