Last week I installed Windows 7 Tray Icons Changer, it's freeware
then I found my notification icons such as wireless, sound, action center icons disappeared
Then I search in many forum for solving this problem, because it was solved by just just click turn it on/off, I found hundred way to try but still not work and I saw many people got same problem so I just see a little post comment but I'm so sorry to put his name here, I forgot that page, so even I tried edit registry or merge them with default windows registry, not work
So I find very simple way from some forum
just go to
Windows/system32/W7TIC there will be three .dll files inside. Copy them into Windows/system32 and restart your computer and they will be back. 

just leave your work here Cool