No display,works after reseating the RAM

For the first time ,this problem occurred and I would like to know the reason behind this.

I use my system mainly for gaming and multitasking.When I was out of station,my brother used PC for internet only(Mozilla Firefox and Internet Explorer,no other programs). It was working perfectly for the first four days with his low usage(not utilizing computer's full potential). Then the strange thing occurred. After installing new version of Mozilla Firefox,computer became slow.Thinking about virus,he performed quick scan in Malwarebytes and suddenly computer became hang and he had to restart PC forcefully and when restarted,there were no display,only power light of CPU lighted and the hard disk light was not blinking.
Then when I returned,I solved this issue just by taking off one ram stick and booted.It was working fine.Finally I put the stick again and it was working again without any issues.

What may be the cause and how I can prevent such problems in future?Does low utilization on a system with high specs affect the system's performance or any other factors?

Is this system very new? If the parts are under a year you might have discovered a bad part. Run MemTest86+ on the system to see if you have a RAM issue.

Layback Bear said:

To answer your question. No
Not using the full potential of your computer will not hurt it.
Doing the memory test as pcunite suggested would be my next move if it was my computer.

I ran memtest86+ v4.20 for almost 7 hours with 10 passes completed with out any errors.
So,does it mean my 2 memory sticks are working fine?What about memory slots?

I have forgot to mention one thing too. Before I left,I changed CPU power cord with another one due to insufficient length. When I returned,I found the end of the wire connected to CPU was quite loose and I think there were no proper earthing.
Does the lack of proper earthing cause excess charges to stay in memory stick?