My Asrock z68 has suddenly stopped responding

I bought a new system. I have been using quite comfortably and even it has been giving me satisfactory desired results. But a few minutes back, I was busy playing game after which I started browsing and chatting and suddenly everything stopped. I was too taken aback to react when I noticed the changes in my computer. The keyboard and mouse has stopped responding but still there is display of the same page I was initially in. I have not touched it after that. I thought I won’t do anything without expert advice. So, I have kept my PC as it is, hung and have logged in via my cell phone looking for an apt solution

That was a smart move. However resetting your PC would have done no harm. I know and understand the fact that you should not take risk with a brand new PC which is just out from his box but you need to understand that minor risks are allowed.

For now, try rebooting your system and post back any change that you can see. I wont be logging out and I’m not expecting you to. Reply quick for better assistance.

You are right, minor risks are allowed but not with my almost-virgin system :P. anyways, as per your instruction, I resetted my computer, the fans were spinning absolutely perfect and surprisingly even my mouse LED lit up. But to my shock, there was no display this time, neither could I enable or disable numlock or capslock on my key board. What does that mean now? The debug code is reported to be A3.

Oh! Your mouse LED let up without your Display being showed up and your keyboard responding says it all. Your system probably crashes down or rather gets stuck at POST. Your debug code being A3 also gives us certain hint about the issue in general.

Before we go ahead, I want you list down the system specification of your computer. Also specify if you have done any overclocking on your system.

Intel Core i5-2400 @ 3.6GHz w/ Hyper 212+ cooler
8GB DDR3 RAM
Sapphire HD 5850 Xtreme (default clocks)
Creative Sound Blaster Audigy 2 ZS
Seagate 7200.11 320GB HDD (primary), WD Green 500GB, Samsung F3 1TB (all SATA)
LG DVD-RW drive (no idea which model)
FSP Aurum CM 650W
Dell ST2410 24" LCD monitor

Let me know if I have missed out on anything, I have not done any overclocking on system. What else do I do? Let me know even if it is a minor or temporary way by which I can start my system so that I can at least move my important files and keep them safe and then call my service agents.

Your specification looks reasonable. Sometime, mis-assembly of hardware configuration can lead to problems but in your case I do not find any such problem. Since, you have not done overclocking also; an error at that end can be ruled out.
What I currently want you to do is reset your CMOS. After which remove your RAM, wipe it on a soft cloth and reinsert it. Check if the system boots, if it does, the first thing that I want you to do other than taking back up is to follow the following steps:

 Press start
 Type ‘Event Viewer’
 Run the application you get in the results
 Note down all the errors and warning message you get in it.