Not detecting windows 7 in a triple booting process

[CelticWarrior]

I wanted to install Ubuntu to get hands on it and then dropping out windows forever after getting well acquainted with the command line
speaking about creating a virtual machine (have bad luck with it.) virtualisations in my laptop are very slow even after assigning around 6 gb of ram (have 8 gb ram) and 2 processors(having 2 cores only and both assigned to the virtual machine)
tried virtual box, VMware player and even VMware pro but the same result

Yeah... NO.
You NEVER assign more than half the host's RAM, ever. It's surprising that it only became "very slow", it should have froze right then and there.
And assigning all the available cores is simply impossible, no hypervisor allows that.

[tea for one]

haven't backed up my data as I am not having hard disk to back it up

Back Up is your first priority - nothing more, nothing less