Windows Update download location

The download location for Windows Updates is:
C:\Windows\SoftwareDistribution\Download

Lock screen background file location

The lock screen background files in Windows 8, 8.1 and 10 can be found in the following folder:
C:\Windows\Web\Screen

System Tray icon DLL locations

Volume:
C:\Windows\System32\SndVolSSO.dll

Action Center:
C:\Windows\System32\ActionCenter.dll

Network:
C:\Windows\System32\pnidui.dll

Power Management for laptops
C:\Windows\System32\batmeter.dll