I've had a copy of windows 7(bought at store,home edition,normal not upgrade) and have been using it for a while now. I activated windows successfully when I first installed it, and it said it was genuine up until now. There now seems to be a water mark in the corner that says it isn't, which is strange because it has been genuine for a long time. My copy of windows is a normal version of windows 7 home edition (x64) bought from a store which I presume has 3 installs. Any reason why windows thinks it is not a genuine copy?