I asked this couple of times in build discussion threads but I haven't received any replies. Therefore, I would like to ask with a thread to get attention. This is my situation: I had installed German Windows TP 10041 Enterprise with Slow Ring ISO I updated it to Windows TP 10049 with WU Now I would like upgrade my German 10049 with, Wzor's leaked ISO file which is Windows TP 10051 and English. I doubt that German 10049 will conflict with English 10051. Has anyone tried this before? Since now in my system only language pack is German, I thought maybe before upgrading I have to install English language pack.