I formatted my system and built it from scratch, that obviously also included SQL Server. I always set SQL Server services (SQL Server Database Service, SQL Server Agent, SQL Server Reporting Service, etc.) to Automatic. This means, when OS gets booted, all these services will also get started before we see Desktop.
I read a KB article on MSFT site, which explained each of Application Startup options; Automatic, Automatic (Delayed Start), Manual, Disabled.
Difference between Automatic and Automatic (Delayed Start) is that Automatic option lets the concerned service to get started immediately after OS boots. Automatic (Delayed Start) option lets all services of OS to get started first and then after a brief delay starts the concerned service.
After reading above, I decided to set SQL Server Services startup option to Automatic (Delayed Start). And that proved disastrous.
Restarting the system never progressed beyond STARTING WINDOWS. And when I switched off system forcibly and rebooted it, system asked me to either BOOT SYSTEM NORMALLY or RUN SYSTEM STARTUP FAILURE DIAGNOSTIC.
Selecting either of above yielded nothing. I had no other option than to reinstall OS.
Moral of this bitter story: Never set Automatic (Delayed Start) as Startup option to all SQL Server Services. If you don’t want these services to be started immediately when OS boots, then set it up to Manual.