Dell Inspiron 5537 OS Crash

Hello,

I have a 2 year old Dell Inspiron 5537. Recently I was having some issues with my OS (Windows 10), so I took backup and reset it from Windows 10's own option in the settings. This model came with original Windows 8.1 which I upgraded to Windows 10 and it did not come with any physical installation media. Now during the reset, the laptop shut down while the reset was at 90% due to the fact that I had taken out the charger and let it run on battery power (you can do this by disabling the battery device from device manager -why i did this? Because my charger was not working). Now when I turn on the laptop it goes to the Dell screen, stays for few seconds, shuts down and again repeats the same cycle. I am fine with reformatting it again but I am confused as to how I can retrieve the original OS without the installation media. Will going to a Dell service centre help me get my OS back for free (Dont want to shell out cash for something I have already 'bought' once before) Please help me out. Any responses are really appreciated. :)