Did you do any hardware upgrades that may have made windows think it is a new machine? RAM or CPU upgrade can trigger it. When this happens, it breaks DRM and system restore. Easy test is to try Netflix, if that is the problem you won't be able to stream anything in it. I don't remember exactly what I had to delete to wipe the DRM and start clean, Netflix support was able to guide me to it pretty quick. Removing the upgrade will fix it as well, but I'm guessing you want to keep whatever you upgraded.
Also, if it is the problem you will probably need to re-add your system drive to the system restore settings (and remove the phantom copy of your system drive that is from the "other machine").