Need advice of gaming performance of new build...

Hi guys. The reason I'm here is to find our why HALO keeps crashing!? I'll be right in the middle of a firefight and POOF, restart-no warning, no errors. I thought I had a decent system that could play decent games. But my system is choking on it. Is a game like HALO demanding a bit much from this configuration?

Here's the specs on my new system foundations (I hope to build on it):

[System Summary]
OS Name:Microsoft Windows XP Home Edition
Version 5.1.2600 Service Pack 2 Build 2600
Activation Status Activation Pending (18 days remaining)
System Manufacturer INTEL_
System Model D945GCR_
System Type X86-based PC
Processor x86 Family 6 Model 15 Stepping 13 GenuineIntel ~1995 Mhz
BIOS Version/Date Intel Corp. NL94510J.86A.0010.2007.0523.1650, 5/23/2007
SMBIOS Version 2.4
Locale United States
Hardware Abstraction Layer Version = "5.1.2600.2180 (xpsp_sp2_rtm.040803-2158)"
Total Physical Memory 1,024.00 MB
Available Physical Memory 536.80 MB
Total Virtual Memory 2.00 GB
Available Virtual Memory 1.96 GB
Page File Space 2.38 GB
I'm using my onboard GPU and I'm using a Western Digital HDD, Model WDC WD3200JB-00KFA0.