How to know who accessed my files in Windows 7?

I use Windows 7 in my office & we use many files to share with others. Usually I can share file and folder and can give user permissions. Many of the users use files from my computer. Some of the users sometimes edit some files and it hard to recover this. No one agrees to doing it.
So I want to know who accessed that file and when he accessed, I want to know who modifies or deletes content from a file. What is the detail pre process?
