[Rehan]

@Rehan!
I think I may have found you a solution to your problem.
I re-read what you wrote in your second post. You mentioned that you did a new installation of Win7-Pro and I assume that you didn't update that system at all. If that's correct, then it's normal that those Trusted Root Certificates (TRCs) are obsolete, they date back to 2007!!..

What you should do is update that system with the latest patches and latest TRCs. I'm not sure if they still support Win7 by now, but take a look at this site:
https://download.wsusoffline.net/

...Or any other way to get those TRCs from.

Good luck!

Actually i have updated my windows. I don't think windows 7 automatically download updates. Because whenever i enable update and try checking for updates. It fails. As Hidden Refuge said windows 7 is no more supported by Microsoft. I manually download essential updates and install them. After that i updated the dot net framework. But still same thing happens.
On the other hand i have some questions in my mind, that how will i be able to use my pc with linux OS. How will i use my .exe programs those are limited to Windows. How will i use Microsoft Office tools, those are essential for my education work. ( i know i can do it online but not as in pc ). What about system Drivers etc.