New computer freezing randomly

Hey i recently bought a new custom built gaming PC and it works fine in terms of performance etc however I have had an annoying problem. I've had the PC for just over a week and on two occasions I have had the problem where the PC would just completely freeze to the extent that I can't open task manager, move the mouse and the keyboard would stop working. Also the Skype call I was in would just stop. This would force me to have to reboot my PC using the button on the tower to shut it down. So far the two occasions have happened when I'm not actually on a game and when the problems did happen I was using two different programs. The first occasion I was on OpenOffice and the second occasion I was just browsing using Firefox so i don't think it is program specific.

The first crash happened two days after owning the new pc, the second crash happened today.

Here are my specs:

Intel Core i5 3570K @ 3.4ghz
8gb 1333mhz ram
Windows 7 64-bit Home Premium
Gainward GTX 660ti
Asus P8Z77-V LX Motherboard
600w Xigmatek PSU

Anyone have any ideas? Is there anyway i could access a crash log?

run memtest

you can run it through your pc Bios if it isn't a overclcoked machine it could be bad hardware Bad RAM

run the MEM test in the bios when you boot the machine if you don't know how to do this and you feel it is to much to do take it back to where you bought it and have them test the ram