Unknowingly to many Windows 7 users, a hidden primary system partition which is active will be automatically and forcefully created by setup during installation of Windows 7. The additional separate standalone NTFS partition, which is not labeled with any drive letter or path, has the size of 200 MB, but only occupy 32 MB of it with 168 MB remains free.

The small 200MB partition actually holds Windows Recovery Environment (WinRE), which only available from DVD installation disc in previous operating system such as Windows Vista (see how to launch WinRE on DVD). The partition holds system files and bootable files that are essential to boot the Windows 7 properly in the event of the need to recover the OS in the event of corruption. The 200MB partition is pretty much similar to many recovery partition that been made on factory installation by most OEMs on the computer they sold.

http://www.mydigitallife.info/2009/01/09/how-to-av oid-200mb-hidden-system-partition-from-been-create d-during-windows-7-installation/