I don't know the legalities of using the icons from other programs, but you can open most EXE or DLL files in Visual Studio (using File-Open) and see a list of their resources.
For instance, opening SHELL32.DLL (found in your windows\system32 folder) gives a list of AVIs, bitmaps, cursors, icons and more. You can right click any of them and choose export (make sure to change the extension to the right one).
Again, I don't know if they're redistributable - I did a search on Google but couldn't find anything which doesn't mean you *can* use them. If you find some you like, you may want to write to MS (or post on one of their official forums) to ask.
-Nerseus