Stuck on trying to install windows 10 after downloading upgrade

[KALAIARASI SETTU]

I would trying to upgrade windows 10 from windows 8.1. It shows download have been successfully completed, but it's stuck during installation showing " preparing for installation". I waited for nearly 3 hours and i then restart the computer. It remains the same. i left for as it few hours. I don't know what was really happened, it starts downloading the windows 10 content once again.
My question is Where is the previously downloaded file? ,
If it present then why download starts automatically once again??
Is there any problem will occur during installation of windows 10 as like first time on completion of second time??

 

[Trouble]

The first thing you need to do is read this
https://www.windows10forums.com/threads/please-for-your-own-peace-of-mind.794/

The second thing you need to do is
Make sure that your computer is currently running all the latest drivers for all you integrated hardware devices and that you do not have any third party security suites installed nor any third party USB attached devices, especially wireless dongles supporting wireless keyboards or mice (Bluetooth, IR, RF). Do the upgrade with a monitor, usb mouse and usb keyboard only attached to your computer.

The third thing you probably should do is
Acquire the actual ISO file yourself, to perform the inplace upgrade and simply mount it from within Windows 8.1 and run setup.exe from it.

The installation media can be obtain through either of these two resources.
https://www.microsoft.com/en-us/software-download/techbench
OR
http://www.microsoft.com/en-us/software-download/windows10