Okay, since your first question is how can I change my system icons in windows 7, the answer is IconPackager found here. Link.
IconPackager works with Icon Packages found in the library here. Link.
The programs WindowBlinds is one of a kind it changes your windows, the task bar, start panel, window frames and much more. It is found here. Link.
The WindowBlinds themes are found in the library here. Link.
Both these programs are available as free 30 day trial versions. After that they stop working. So, give them a try and if you like them buy Object Desktop which gives you both these programs and many more. You can find Object Desktop here. Link.