Those sites are simply ISO downloads for people who bought keys legit online from Microsoft and needed a different download link for there copy of Windows. Those sites give a copy of the operating system but not a key to run the system past the 30 free evaluation days. You can go to the Microsoft online store to purchase a legal key.
Here is the link the the Microsoft Store's Windows 7 Pagehttp://www.microsoftstore.com/store/msstore/list/parentCategoryID.44066700/categoryID.50726100
Also, the 30 dollar deal for college students ended a while ago, you can purchase an Upgrade version of Windows 7 Professional edition for around $60 now.