If you upgraded your curent Vista installation to new Windows Seven ,even if you install windows 7 on another partition the old data of previous operating system still present on your hard drive and becomes undeletable or inaccessible from Windows 7.
Usually this problem of undeletable files and folder is security related and can be fixed easily by changing folder security settings , but in this case object is associated with SID of old operating system user accounts and these users are no longer exist in your present installation of windows 7.
In order to access the files and folder for, we will need to take control (change ownership) of the files under Windows 7.
Here are two command line syntaxes to instantly take ownership of such files and folders
For Files:
takeown /f file_name /d y
icacls file_name /grant administrators:F
For Directories:
takeown /f directory_name /r /d y
icacls directory_name /grant administrators:F /t
