• Program Files. This is where all the files for any programs and software you install in Windows 7 sit. There are two Program Files folders in the 64-bit version of Windows 7: Program Files x86 for 32-bit software and Program Files for newer 64-bit software. Each program sits in its own custom folder under one of these folders. In the 32-bit version, there is only a Program Files folder.
• Users. This is where, by default, all of your documents and files sit, and it is also the location of the Windows registry, the database of settings for Windows and your software. Within the main Users folder, there is one subfolder for each user and another folder called Public, where shared files and folders are kept. There are also hidden user folders called Default and All Users.
• Windows. This is the main folder into which the operating system is installed.
Windows also installs hidden system files across the disk, including the Root folder.
These hidden files and folders are where Windows stores operating system recovery software and folders to support legacy software, including Documents and Settings and the Autoexec.bat and Config.sys files that date back to the earliest versions of DOS.
Inside the main Windows folder are a great many different folders, some of which exist to maintain compatibility with legacy hardware and software and some of which service specific features within the operating system.
All of these files and folders are essential, and you should not move, rename, or delete any of them. Folders you might find of particular interest include the following.
• Globalization. This is where you will find the desktop wallpapers in Windows.
• Resources. This is a similar folder to Globalization but is for Windows desktop themes.
• System32. The main operating system files, including hardware device drivers, are located in this folder.
Source of Information : Microsoft Press - Troubleshooting Windows 7 Inside Out