Core i7 quad, GT540, bluray, 750 gig hd, 8 gig ram, some issues in BUNYA, Queensland for sale

For sale I have an acer laptop with the following specs:
* core i7 quad core
* nvidia GT540 2 gig graphics
* 15.6 inch widescreen
* 750 gig hard drive
* 8 gig ram
* bluray reader / dvd burner
* webcam
* wireless
* genuine windows 7
* microsoft excel and word 2010
It worked reliably for me doing normal stuff including watching movies, and I sold it to someone, but they found it restarted at a particular point in a game they played. So I gave them their money back.
I'm not sure what the problem is - hardware or software - although I have reinstalled the operating system. I have run a 'stress test' program on it and it does not fail, so I don't know what the story is.
So now I'm selling it as 'faulty', at cheaper price. It might be fixable, or even meet your needs as is.