Why does my new ACER Veriton M6630G PC struggle to run games or crash?

I have recently bought a new desktop PC (Acer Veriton M6630G) to play games on. Despite all the specifications being pretty high, it struggles to run pretty much any game nicely. It can run Hearthstone although often crashes before managing to load it up. I tried running cities skylines but it all feels a bit slow with the mouse dragging behind and with the skiing game "Snow", its laggy and slow. I'll post the specifications below. All I can think is that maybe the graphics card can't handle it. Any help would be great. Thanks.
CPU-Intel core i7 processor 4770 RAM-8GB DDR3 Memory HDD-1TB Hard Drive Video-NVIDIA GeForce GT620 1GB

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-Justin

AcoustiCalness,

The only thing I can think is that the game graphic settings are set high, try and lower some of the settings and see if that improves it.

AcoustiCalness

Thanks for the reply but I tried that as soon as the problem occured. I've tried running the games on as low res as possible and it's no use. I just thought that the PC had such high specifications that I wouldn't encounter this sort of problem.