In your system configuration it is mentioned "Configuration: Windows 7 / Internet Explorer 8.0", so I assume your computer has Windows 7. Please try the steps mentioned below and reply with results:
1) Start Windows 7 with an account that has administrative privileges or at least privileges to change the power settings for the account.
2) Click Start > Control Panel and click the link titled Appearance and Personalization.
3) Click the link titled "Screen Saver". In the Screen Saver Window that opens, click "Change Power Settings" link at the bottom of the window.
4) Click "Change Plan Settings" link next to the selected power plan.
5) Click "Change Advanced Power Settings".
6) In the center of the window, scroll down until you see an option titled "Power Buttons and Lid". Click on the plus symbol next to it and then click on the plus symbol to expand the option titled "Power Button Action". Finally, click the link labeled "Shut Down".
7) Choose "Do Nothing".
8) Click the "OK" button.
9) You need to make this change for every account on your PC.
10) This eliminates the chances of computer shutting down if the power button is accidentally pressed or is faulty.
The shutdown can occure because of a high temperature of your graphic card or cpu. Some computers shutdown the computer as a security when the heat of the cpu or the graphic card is too high to prevent damage.
Maybe you have dust on the CPU fan or the graphic card fan that prevents the heat from evacuating correctly.
To clean the fans, you must use an air pressurised spray can. If the shutdown still happens after the cleaning, the other options are graphic driver problem which makes the computer crash when a specific graphic information of the game goes through the graphic card. A driver update of the Graphic card can help sometimes.
The last option could be a problem with your power supply. Maybe your configuration asks too much power for your configuratoin especially when you play games. So their is an electrical crash of your power supply which could explain the shutdown.