Big Big trouble, plz help me, blue screen T_T

Hi all here. I hope some real 'guru' can help me discovering the source of this error.

First of all I paste here a link on the screenshoot of this error:
http://img.photobucket.com/albums/v...do/9804c273.jpg

If the page does not show try refreshing 2 or 3 times.

Now details about my system:
CPU(s)
Number of CPUs 2 (1 Physical)

CPU#1 APIC ID = 0
CPU Name Intel Pentium 4
Name Intel Pentium 4
Code Name Prescott
Specification Intel(R) Pentium(R) 4 CPU 3.20GHz
Family / Model / Stepping F 3 4
Extended Family / Model 0 0
Package mPGA-478
Core Stepping D0
Technology 0.09 µ
Supported Instructions Sets MMX, SSE, SSE2, SSE3
CPU Clock Speed 3207.4 MHz
Clock multiplier x 16.0
Front Side Bus Frequency 200.5 MHz
Bus Speed 801.8 MHz
L1 Data Cache 16 KBytes, 8-way set associative, 64 Bytes line size
L1 Trace Cache 12 Kµops, 8-way set associative
L2 Cache 1024 KBytes, 8-way set associative, 64 Bytes line size
L2 Speed 3207.4 MHz (Full)
L2 Location On Chip
L2 Data Prefetch Logic yes
L2 Bus Width 256 bits

CPU#2 APIC ID = 1
CPU Name Intel Pentium 4 (logical unit)


Mainboard and chipset
Motherboard manufacturer ASUSTeK Computer Inc.
Motherboard model P4P800-E, Rev 1.xx
BIOS vendor American Megatrends Inc.
BIOS revision 1004.001
BIOS release date 09/24/2004
Chipset Intel i865P/PE/G/i848P rev. A2
Southbridge Intel 82801EB (ICH5) rev. 2
Sensor chip Winbond W83627THF
FSB Select 533 MHz
Performance Mode enabled
Graphic Interface AGP
AGP Status enabled, rev. 3.0
AGP Data Transfert Rate 8x
AGP Max Rate 8x
AGP Side Band Addressing supported, enabled
AGP Aperture Size 256 MBytes

Memory
DRAM Type DDR-SDRAM
DRAM Size 1024 MBytes
DRAM Frequency 200.5 MHz
FSBRAM 1:1
CAS# Latency 2.5 clocks
RAS# to CAS# 3 clocks
RAS# Precharge 3 clocks
Cycle Time (TRAS) 6 clocks
# of memory modules 2
Module 0 Infineon DDR-SDRAM PC3200 - 512 MBytes
Module 1 Infineon DDR-SDRAM PC3200 - 512 MBytes

Software
Windows version Microsoft Windows XP Professional Service Pack 2 (Build 2600)
DirectX version 9.0c


What I get is that sometimes the computer reboots sayng that the system has been recovered from a serious error.

I formatted times and times, mb bios is updated...but I can't get why this error occurs. What can I do ?

Please help me discovering that, I am desperate...also because this pc is the result of 3 month of summer works T_T.

I pray you gurus...help this italian boy plz.


p.s. again, if the file says forbidden, try closing and open the url again or try "save object as". The file is a simple jpg screenshoot of the error.

p.p.s. I did memtest86 and I stopped it after 2.50h of work at the beginning of pass 9 and got 0 errors.