Icons Question [Change default program icon]

I am customising a program and have changed the default desktop icon that is shipped with the exe file using "Resource Hacker ", a freeware tool for accessing icons and bitmaps within executable files.

However, I have not been able to change the small icon that Windows uses for this program that appears in the very top left hand window bar - this is also true of the small icon that Windows uses for the program in the lower task bar.

So is it possible that this icon is being cached in the registry somewhere? I have been through all the DLLs and EXE files that came with the application using "Resource Hacker" and cannot find anywhere where this small icon is held.

Any help much appreciated.