I've recently bought Radeon HD7770 for my HP Pavilion Elite HPE.

Except the graphics card, nothing is changed.

Whenever I play any games that require high graphics, the display driver stops without any reason. 

The computer is fine when I am on desktop or playing low graphic games.

I'm suspecting something wrong with graphics driver..

I am having the same issue since an update to the drivers in mid to late Jan. I am running crossfired 7770's and when I try to watch something on XBMC while playing a game, the video driver will stop working. I have updated everything on my system including switching to the newest versions of amd drivers and XBMC program.

Sounds like your power supply, but who knows? You need to read the sticky about posting and furnish the requested information.  Depending on what version of the 7770 you have ...AMD suggests a 450-500 watt PS.  http://www.amd.com/us/products/desktop/graphics/7000/7770/Pages/radeon-7770.aspx#3

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