Sudden Reboot during games

[Connor]

Hey guys.

So my dad has a pretty powerful machine. GTX970 with an I7 (One of the newer ones) yet he's having a persistent problem. During when he's playing games, such as Titan Fall, Planets vs Zombies Garden Warfare and World of Warships, his computer suddenly decides to switch of and reboot. Almost like you've switched the power off at the wall and then quickly put it back on. Does anyone have any ideas on what could cause this? Do you need to know any more information? If so I'll try and provide it.

Thanks.

Edit: Forgot to mention. We've tried several things.

1) We've tried turning off the integrated graphics to see if it's the 970 at fault. It still happens.

2) We've had reports that it could be the power supply yet the manufacture (When it was brought) said it's fine. 650Ws. Is there any way we can test this without buying a better power supply?

3) He's recently tried to install an update but it failed and won't ever reinstall.

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