O que você está vendo é uma sobra no gerenciador de inicialização do Windows.
Cite o link sobre como removê-lo:
In Windows XP you need to edit C:\boot.ini and delete the Ubuntu/Wubi
line. Alternatively you can modify the boot menu via Control
Panel > System > Advanced > Startup and Recovery and pressing "Edit".
For Windows 98 you have to edit C:\config.sys and remove the Wubi block.
For Windows Vista/7, you can use the built-in bcdedit command or install
EasyBCD to edit the boot menu. To use bcdedit, run cmd.exe as an
administrator, then enter bcdedit to show all boot entries, note the {GUID}
specified for the Ubuntu entry, and then remove it: bcdedit /delete {GUID}