...did you run Windows Memory Diagnostics Tool: http://www.geekstogo.com/forum/Windows-Memory-Diagnostic-Tool-t177564.html?
--------[ EVEREST Home Edition (c) 2003-2005 Lavalys, Inc. ]------------------------------------------------------------
Version EVEREST v2.20.405
Homepage
http://www.lavalys.com/ Report Type Quick Report
Computer DEL-PC
Generator Del
Operating System Microsoft Windows Vista Home Edition 6.0.6000 (WinVista Beta)
Date 2009-02-16
Time 18:56
--------[ Summary ]-----------------------------------------------------------------------------------------------------
Computer:
Computer Name DEL-PC
DirectX 4.09.00.0904 (DirectX 9.0c)
Operating System Microsoft Windows Vista Home Edition
OS Service Pack -
User Name Del
Motherboard:
BIOS Type AMI (07/24/08)
Communication Port Communications Port (COM1)
CPU Type 2x , 2400 MHz (7 x 343)
Motherboard Chipset Unknown
Motherboard Name Unknown
System Memory 3200 MB
Display:
Video Adapter NVIDIA GeForce 7100 / NVIDIA nForce 630i
Video Adapter NVIDIA GeForce 7100 / NVIDIA nForce 630i
Monitor Generic PnP Monitor [NoDB] (F5UC5A0137396)
Multimedia:
Audio Adapter High Definition Audio Controller [NoDB]
Storage:
IDE Controller Standard Dual Channel PCI IDE Controller
IDE Controller Standard Dual Channel PCI IDE Controller
SCSI/RAID Controller Microsoft iSCSI Initiator
Floppy Drive Floppy disk drive
Disk Drive MAXTOR STM3500320AS ATA Device (465 GB, IDE)
Optical Drive Optiarc DVD RW AD-7201S ATA Device
SMART Hard Disks Status OK
Partitions:
C: (NTFS) 476937 MB (360912 MB free)
Input:
Keyboard HID Keyboard Device
Mouse HID-compliant mouse
Mouse Microsoft PS/2 Mouse
Network:
Network Adapter NVIDIA nForce 10/100 Mbps Ethernet (192.168.1.101)
Peripherals:
Printer Microsoft XPS Document Writer
USB1 Controller Standard OpenHCD USB Host Controller [NoDB]
USB2 Controller Standard Enhanced PCI to USB Host Controller [NoDB]
USB Device Digidesign Mbox 2 Audio Driver
USB Device Digidesign Mbox 2 Firmware Updater
USB Device Digidesign Mbox 2 Midi Driver
USB Device Evolution MK-449C USB Driver
USB Device USB Composite Device
USB Device USB Composite Device
USB Device USB Composite Device
USB Device USB Human Interface Device
USB Device USB Human Interface Device