abbodi, what you say is true, hotfixes don't appear in "installed updates", but it doesn't seem important to me. In fact, checking files installed with the original .msu file and those installed with the modded .cab file, I found that they are equivalent. x86 version was easiest; I took inspiration in ArnisLav's post on MSFN board. He suggested to change allowedOffline="false" to allowedOffline="true" in "update.mum", but this change corrupted installation. Then I looked in .mum file and I noticed that "exclusive="true"" could be responsable of failure. Changing "exclusive="true" allowedOffline="false"" with "exclusive="false" allowedOffline="true", it worked fine! x64 version was hard to mod; the simply "exclusive="false" allowedOffline="true" was not enough. I had gotten stuck, until I found dism.log file. Then, analizing it, I was able to find errors and I reconstructed a working hotfix.