Screen and computer completely freezes.

I just purchased this new computer and the specs are below. After a few minutes of booting up, the screen completely freezes and the computer completely locks up.

Why is it doing this? or any suggestions from people that have had this problem?

                   WD 740GD RAPTOR 74GB SATA 10,000RPM      

RM-305-104 DDR2 CORSAIR VS512MB PC5200 667MHZ
CS-218-102 BLACK X-PLORER BLK/BLK 420W PS
CD-124-145 BLACK SONY 16X DVDRW DW-Q28A DUAL
CABLE-201-101 24" IDE ROUND CABLE WITH 3 HEADS
CS-WATERCOOL COOLER MASTER LIQUID COOLING KIT
FD-104-102 BLACK MITSUMI 1.44MB FLOPPY
KB-110-107 BLACK LOGITECH OFFICE PRO KEYBOARD
MO-106-101 PS2 BLACK COLOR INTERNET MOUSE
MD-102-127 LUCENT V.92 PCI MODEM
MB-304-104 ASUS P5ND2-SLI DELUXE SKT 775 DDR2
SW-120-123 WINDOWS XP PRO x64 EDITION
CABLE-PROWIRE PROFESSIONAL CABLE WIRING
MISC ONBOARD 7.1 SOUND
SK-102-102 SPEAKER 600WATT PMPO W/ SUBWOOFER
ZD-102-104 BLACK 250MB INTERNAL ZIP DRIVE
VC-146-106 CHAINTECH GEFORCE 6200TC SUP 256MB
PS-109-105 TIT/BLUE X-CON 500W ATX PS ULT31562
CU-173-101 INTEL PENT 840EE DUAL 3.2GHZ RETAIL

Monitor: Philips 109B

Windows x64 edition is still unstable and we don’t recommend it for users. not only that drivers are not in abundance and so downgrading to 32bit will be better for now.

If this a newly purchased computer from a proper ‘dealership’ I would take it back and will not mess with any aspect of it.

You do not want to void any warranties you have.

Even if it was bought from an independent system builder, if it is that new (and probably cost a bit), he/she should cover these sort of teething problems.

I would go back to them first.