thank you Hamza for the reply.
I do have a spare drive (even Hard disk, which I use to store data only 2TB; Secondary & the one I use to install OS 500gb; Primary).
After hitting Install, it didn't ask much of the setting, it restarts couple of time.
The disk partition I had Win7 installed on was around 82+ GB (c drive), I made another 80+ GB (d drive) for the new win8 OS. [Though 30gb is enough for the OS but I didn't want to be worried for the years to come so I allocated more room anyways]
If I can provide any info. which might require, please let me know.
By the way, Before win8 installation, the c drive was 55+gb free out of 82+gb (with programs installed i.e.; around 27gb used).
Now After win8 installation, it still show about 55gb free out of 82gb, which made me thnk that win7 might me recovered. and yes I opted for keeping files while installing the win8. (if this helps !)