Error installing windows 7 on virtual box
Select a virtual machine by clicking its name in the VirtualBox window
Click the Machine menu at the top of the VirtualBox window, and click Settings
Click the Storage category in the Settings window
Right-click in the storage tree pane, and click Add Floppy Controller
Right-click the Floppy Controller device, and click Add Floppy Device
Click the Choose Disk button in the prompt window that appears
Navigate to the floppy disk image file (.IMG) on your computer and double-click it


If that doesn't work, try renaming the .IMG as .ISO and mount it.

If that too doesn't work, use VBoxManage's convertfromraw command as follows:

VBoxManage convertfromraw -format VDI [filename].img [filename].vdi


Mount the VDI as a disk.