How can I back up my pre-installed Windows 8 before installing Ubuntu 13.04?

I want to install Ubuntu 13.04 alongside Windows 8 on my laptop (Toshiba L850/046 with pre-installed Windows 8). I want to be able to pick between the two operating systems at startup.

Also, how can I backup my Windows 8 software? If something went wrong (for example my Windows 8 / hard drive got wiped out), how would I be able to re-install Windows 8 from the back up?

P.S. I plan on installing Ubuntu with a DVD -- that means I don't have to make new partition spaces and can just click the Install alongside Windows 8 option, right?

If your laptop came with a preinstalled windows 8 there must be some sort of utility included to create backup disks. Just use that software to take a backup of your windows 8. However these backup may not keep your windows os settings in case of a re-installation.

[Advanced: If you can explore the hidden drives (by running diskmgmt.msc), you will see *.wim images in there, those are the windows deployment packages. You can save them also, but restoring them is a little bit complex method]

Second option is to use any cloning software to clone your hard disk to an external driver. But this usually requires the external drive capacity should be same as your laptop.

Installing ubuntu in preinstalled windows 8 is lot more complecated. Thanks to the secure boot requirement of preinstalled windows 8 PC. You can go through the link below to have a guide on how to proceed with instillation..

Installing Ubuntu Alongside a Pre-Installed Windows with UEFI