Windows XP SP2 + GA-MA78GM-S2HP = DEATH

I got a new assembled pc about two weeks back.From the first day when I installed winxp sp2,it is giving me a lot of problems.Sometimes the mouse and keyboard freezes and there is no response from the pc.Sometimes I get a B.S.O.D saying "IRQL not less or equal".Some times I get a B.S.O.D with the error 0x0000007F stating beginning dump of physical memory.
I ran memtest86+ for an hour to check whether it is a faulty RAM,but there were no errors.I did a clean installation of Win Xp thrice but to no avail.All the drivers are updated.
Ubuntu 9.04 works fine without any issues.
Here are the specifications of my pc.
Processor(s)

Number of processors 1
Number of cores 2 per processor
Number of threads 2 per processor
Name AMD Athlon 7750 Black Edition
Code Name Kuma
Specification AMD Athlon(tm) 7750 Dual-Core Processor
Package Socket AM2+ (940)
Family/Model/Stepping F.2.3
Extended Family/Model 10.2
Brand ID 6
Core Stepping DR-B3
Technology 65 nm
Core Speed 2705.9 MHz
Multiplier x Bus speed 13.5 x 200.4 MHz
HT Link speed 1803.9 MHz
Instruction sets MMX (+), 3DNow! (+), SSE, SSE2, SSE3, SSE4A, x86-64
L1 Data cache (per processor) 2 x 64 KBytes, 2-way set associative, 64-byte line size
L1 Instruction cache (per processor) 2 x 64 KBytes, 2-way set associative, 64-byte line size
L2 cache (per processor) 2 x 512 KBytes, 16-way set associative, 64-byte line size
L3 cache (per processor) 2 MBytes, 32-way set associative, 64-byte line size

Chipset & Memory

Northbridge AMD 780G rev. 00
Southbridge ATI SB700 rev. 00
Memory Type DDR2
Memory Size 2048 MBytes
Memory Frequency 334.1 MHz (3:5)
CAS# Latency (tCL) 5.0 clocks
RAS# to CAS# (tRCD) 5 clocks
RAS# Precharge (tRP) 5 clocks
Cycle Time (tRAS) 15 clocks
Bank Cycle Time (tRC) 20 clocks
Command Rate (CR) 1T

System

System Manufacturer Gigabyte Technology Co., Ltd.
System Name GA-MA78GM-S2HP
System S/N
Mainboard Vendor Gigabyte Technology Co., Ltd.
Mainboard Model GA-MA78GM-S2HP
BIOS Vendor Award Software International, Inc.
BIOS Version F2
BIOS Date 10/30/2008

Memory SPD

Module 1 DDR2, PC2-5300 (333 MHz), 2048 MBytes, Transcend Information

Software

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