Mine has gone as well. I think that what happens is that the update is downloaded and installed (manually this time, but I suspect it will subsequently be automatic). This program is then executed according to its schedule. The first time, it checks certain system files against its database to make sure that they are genuine. If they are, your computer successfully passes validation. If not, your computer fails validation and is flagged as non-genuine. If this happens, you can follow the on screen instructions to restore your system's genuine status. About a week after this first run, the program runs again. This time, it gathers information about certain files which are then used to update the program's definitions. This should prevent the likelihood of too many false positives, and will also take into account the new hacks and activation exploits that are around. These are sent anonymously to Microsoft and then the program is automatically deleted as it has now done its job for this current period. About 3 months later, the whole process will be repeated. A new version of the program will be downloaded and installed. This will include new definitions as defined by the information received by Microsoft from the second running of this program on the previous occasion. This timescale is subject to change by Microsoft and may possibly change from time to time..
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