OK, firstly you will need a good quality USB drive, download the latest image for the VU+Duo.
When you have the image on the USB just insert it into the VU+ (whilst it is powered off), power on the VU and press the power button when you get the message on screen.
Just wait and let the flash happen then set the box up again using the menu.
If you had a line/gift and it is still on your box without you having a back up then you will need to contact your supplier to get a replacement one or a new one.
I have a VU+ Solo 2 and they are a great box.