Accidentally formatted setup of a pre-installed Windows 8.

I accidentally formatted a pre-installed Windows 8 setup (formatted the entire hard drive). As it was pre-installed, I didn't get the installation disk as well. Is there any way by which I can retrieve somehow my Windows back?

How did you do it? You can only format it from an external system (Win PE, installation disk, another OS). You can't format your boot drive while Windows is running.

Depending how you did it, perhaps you can - it depends really if you just destroyed the partition table or overwrote the disks contents.

While installing Ubuntu(I needed both the OS), I formatted the partition entirely.

Try to download this from another PC GParted -- Live CD/USB/PXE/HD and boot it as live (USB or CD). Don't use the PC you formatted the partition on as you'll overwrite more and be to recover less. See the manual here GParted -- GParted Manual

Good luck. It is a shame it is so easy to do. In the worst case you can re-install windows but try to get your data back first if you need it.

I'm sorry as I was OS-less, I have already installed Ubuntu. Hopefully I've not committed a blunder.