You have installed the Windows Recovery console on your computer. When you attempt to install SDE on the computer, SDE identifies the recovery console as an additional operating system.
Sophos product and version
Sophos SafeGuard Disk Encryption
What to do
When you install the Windows Recovery Console, your boot.ini file is edited to include an option to boot to the Windows recovery console.
Remove the Windows recovery console from your computer. The Windows Recovery Console is considered a separate operating system: installing SDE on a computer running more than one operating system is not supported by Sophos. For instructions on removing Windows Recovery Console, please see http://support.microsoft.com/kb/555032.