From my own experience, it seems that the Microsoft Compatibility Appraiser scheduled task does nothing if it has already been run in the last 24 hours. To force the task to actually perform the check again, you have to convince it that more than 24 hours have passed by changing the windows date & time settings to a future date (e.g. tomorrow). If you then run the task again, wait roughly 15 minutes* and then open the upgrade dialog from the system tray, you should see that the data has now been updated. Don't forget to set the clock back to the correct date and time afterwards.