[help] Is there any way to work on Explorer.exe file

I have seen some application which creates tabs in explorer like we have in browsers I wonder how they are able to make changes in programs like these.

I am currently working on Windows 7 64 bit and I too want to learn how to modify explorer.exe according to my neeed. Any documentation or any help will be appreciated.

I found that BHO can help me but I am good to learn with Scratch can any one help with this.........I am trying to modify Preview Pane of Explorer