Thanks for your reply mooms. It inspired me to have another try, and this time the final ISO was 4.3GB. This time I used Wintoolkit to extract files from the original Windows 7 SP1 ISO. Previously I had used Windows 8 to mount the Windows 7 Sp1 ISO, and copied those files into a folder for Wintoolkit. Maybe that created the problem? Just to answer your question, I was only using the updates from here, plus the Slim Microsoft .NET Framework 4.5.2 Full x86/x64. http://www.wincert.net/forum/topic/12103-16-juin-2015-update-list-gdr-pour-windows-7-sp1-x86x64-fr-en-de-es-it/