You got a stubborn board on your hands. Maybe clearing the RTC RAM may help. See section 2.7.2 (page 2-19) of the manual. Boot directly to the A:\ drive and try a reflash again. I see you have a P4C800 Deluxe. However, my board is a P4C800-E Deluxe and the 1016 BIOS fixed the issue for me. If all else fails, RMA it for a P4C800-E. Here's my info:
CPU-Z version 1.22.
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 3
Extended Family / Model 0 0
Package mPGA-478
Core Stepping C0
Technology 0.09 µ
Supported Instructions Sets MMX, SSE, SSE2, SSE3
CPU Clock Speed 3519.7 MHz
Clock multiplier x 16.0
Front Side Bus Frequency 220.0 MHz
Bus Speed 879.9 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 3519.7 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 P4C800-E, Rev 1.xx
BIOS vendor American Megatrends Inc.
BIOS revision 1016.001
BIOS release date 02/23/2004
Chipset Intel i875P rev. A2
Southbridge Intel 82801EB (ICH5) rev. 2
Sensor chip Winbond W83627THF
FSB Select 800 MHz
Performance Mode disabled
AGP Status enabled, rev. 3.0
AGP Data Transfert Rate 8x
AGP Side Band Addressing supported, enabled
AGP Aperture Size 128 MBytes
Memory
DRAM Type DDR-SDRAM
DRAM Size 512 MBytes
DRAM Frequency 146.7 MHz
FSB

RAM 3:2
CAS# Latency 3.0 clocks
RAS# to CAS# 4 clocks
RAS# Precharge 4 clocks
Cycle Time (TRAS) 8 clocks
# of memory modules 1
Module 0 DDR-SDRAM PC3200 - 512 MBytes
Software
Windows version Microsoft Windows XP Workstation Service Pack 1 (Build 2600)