Precision T5500 hanging & restarting issue

Hi,

I just bought Dell T5500 Tower workstation and I cannot understand what`s going on.

Quick spec for your reference:

PROCESSOR - Intel XEON QUAD CORE X5687 4x3860Mhz (3.6Ghz, 12MB Cache);

RAM - 24 GB DDR3, 1066 MHz;

VIDEO - 2x ATI RADEON FIREPRO V5900 - 2GB DDR5

HDD - 500GB SATA 7200RPM (3,5") ;

SYSTEM - WIN 7 PROFESSIONAL (X64);

At my first system start I was able to use it only for 3 minutes, after that mouse indicator stopped responding and then immediate restart followed. I tried on and on with same result. I then tried to follow one`s advice and loaded default bios settings (my BIOS version is A09) Result is a that I can`t even get to the Win 7 now. It just stops after quick blink with some BSoD (please see pictures attached). I tried to:

a) uninstall ATI CATALYST drivers with no result - system hanging and immediate restart after system start

When I do diagnostic it hangs on an exact moment when it processes a memory tests (please see picture attached)

BSoD picture link:

https://www.dropbox.com/s/lxzum3juxjmlmoj/20150414_155813.jpg?dl=0

Diagnostic picture:

https://www.dropbox.com/s/mkcjmnvapuad8aj/20150415_002651.jpg?dl=0

Can anyone help me? What should I do ? 

Regards