New Build's Locked up twice now

Hello, im relitivly new to PC building. I'll post my specs below. Everything seems to be fine, but I twice now i've had steam installing a few games, and SWTOR installer up and my system will lock up. Only two games updating on steam, not much stress. The tower sounds normal, fans keep going and so on. But my screen locks up and i cant use my keyboard/mouse. Any ideas?

Case: CM Storm Trooper
CPU: Intel Sandy Bridge Extreme Edition 3960x
Mobo: Asus Rampage IV Formula
Ram: G.SKILL Ripjaws X Series 32GB (4 x 8GB)
HDD: Seagate Barracuda ST3000DM001 3TB 7200 RPM SATA 6.0Gb/s 3.5
PSU: Thermaltake Tough Power 1475w

Hi

If you have overclocked your pc, try removing to see if this makes a difference.

If not, have a look at event viewer - type event viewer in windows search box. See if that gives you any clues.

If there are error messages in there, they can be googled as they usually are a bit obscure.

Also, if you are using Daemon Tools, you can sometimes experience the problems you are having, so check their support forum if so.

very first thing to do is get memtest and do a few test runs off a bootable usb or cd, rule out any problems with the ram because it's always the most likely cause of problems.

Secondly make sure all your drivers are up to date, everything else that could cause that problem is very rare, so rule out the common problems first.

EDIT: memtest: http://www.memtest.org/#downiso easiest option is the usb autoinstaller if you have a spare pen drive.

What graphics card do you have installed in the system?