I've seen that happen with several Version Upgrades over the last decade or so, seems when the Registry is written/rewritten during the install that things not actually saved to the HDD do get 'lost', just one of those things we have to deal with. To explain further, the Registry is made of up 5 Hives [editable text files] necessary for Windows to know how to run itself. Editing those files is not for everyone to do, make one mistake and Windows can become unusable.