You must create a bootable usb stick with imagen.iso.
For this task, you can use this program:
http://www.pendrivelinux.com/downloads/Universal-USB-Installer/Universal-USB-Installer-1.9.5.6.exe
This program, as stated on their site:
http://www.pendrivelinux.com/universal-usb-installer-easy-as-1-2-3/
Demand:
USB stick Fat16/Fat32/NTFS formatted
Universal-USB-Installer-1.9.5.6.exe
Windows XP/Vista/7/8
PC with a BIOS that can boot from USB
Linux image.iso
The procedure is as follows:
Download and install a Universal-USB-Installer-1.9.5.6.exe
Run it
Select Ubuntu from the dropdown list.
Press Browse and open the downloaded image.iso
Choose the USB stick and press Create