These instructions initially appeared at this url: http://blog.aproductofsociety.org/?p=13 but have since disappeared.
As is mentioned on my primary blog with instructions for Windows 7 and Windows Vista, unfortunately, in order to complete this process you need an existing Windows installation.
1. Download Vista SP1/2008/Windows 7 x64 ISO from MSDN (Microsoft), or grab your CD
2. Create 3 folders c:\efi-iso c:\efi-exe c:\efi-dvd
3. Download oscdimg.exe from here and extract into c:\efi-exe
4. Extract iso using 7-Zip or WinRAR (Or copy the contents of the DVD) into c:\efi-dvd
5. Start up a command prompt (Start -> Run -> cmd)
6. Type: cd c:\efi-exe
7. Type: oscdimg -n -m -bc:\efi-dvd\boot\etfsboot.com c:\efi-dvd c:\efi-iso\windows7.iso