Windows PCs have many .dll resource files that contain number of icons. Here are some of them. 

C:\Windows\System32\shell32.dll

C:\Windows\System32\compstui.dll

C:\Windows\System32\DDORes.dll

C:\Windows\System32\ieframe.dll

C:\Windows\System32\imageres.dll

C:\Windows\System32\mmcndmgr.dll

C:\Windows\System32\netshell.dll

C:\Windows\System32\wmploc.dll

C:\Windows\System32\pifmgr.dll

This is taken from a Windows 7 PC, but most of these .dll files will be available in other Windows versions as well.