if youre using apple then you're screwed (no really... you're just screwed for using apple 
)
otherwise they are in.... no idea :p
i think they are the fti files in the icons folder of the installation directory
if you want to change the icons you have to make you're own
it's as easy as opening up MSPaint and saving something as a bmp
ok, maybe not that easy because you need to know the dimensions 32x32 pixels i think..
that's a "Ch" pronounced as a "K"
Computer skills I should have:
Objective C, C#, Java, MEL. Python, C++, XML, JavaScript, XSLT, HTML, SQL, CSS, FXScript, Clips, SOAR, ActionScript, OpenGL, DirectX
Maya, XSI, Photoshop, AfterEffects, Motion, Illustrator, Flash, Swift3D