here's a full list of my system.
 if you could let me know if there's info missing. or you see somthing wrong

SiSoftware Sandra
Computer
Model : Supermicro X7DA8
Workgroup : WORKGROUP
Host Name : Rack64-PC
User : Rack 64
Processor
Model : 2x Intel(R) Xeon(R) CPU            5160  @ 3.00GHz
Speed : 3GHz
Cores per Processor : 2 Unit(s)
Threads per Core : 1 Unit(s)
Type : Dual-Core
Integrated Data Cache : 2x 32kB, Synchronous, Write-Thru, 8-way, 64 byte line size
L2 On-board Cache : 4MB, ECC, Synchronous, ATC, 16-way, 64 byte line size, 2 threads sharing
Computer
Mainboard : Supermicro X7DA8
BIOS : Phoenix Technologies LTD 6.00 10/02/2006
Bus(es) : X-Bus PCI PCIe IMB USB FireWire/1394 i2c/SMBus
Multi-Processor (MP) Support : 2 Processor(s)
Multi-Processor Advanced PIC (APIC) : Yes
Total Memory : 8GB DDR2 FB-DIMM
Chipset
Model : Super Micro Computer 5000X Chipset Memory Controller Hub
Front Side Bus Speed : 4x 333MHz (1.33GHz)
Total Memory : 4GB DDR2 FB-DIMM
Channels : 4
Memory Bus Speed : 2x 333MHz (666MHz)
Memory Module(s)
Memory Module : Kingston 1GB ECC DDR2 FB-DIMM PC2-5300F DDR2-666 (5-5-5-15 3-20-5-3)
Memory Module : Kingston 1GB ECC DDR2 FB-DIMM PC2-5300F DDR2-666 (5-5-5-15 3-20-5-3)
Memory Module : Hynix (Hyundai) HYMP525F72BP4N2-Y5 1GB ECC DDR2 FB-DIMM PC2-5300F DDR2-666 (5-5-5-15 3-20-5-3)
Memory Module : Hynix (Hyundai) HYMP525F72BP4N2-Y5 1GB ECC DDR2 FB-DIMM PC2-5300F DDR2-666 (5-5-5-15 3-20-5-3)
Video System
Video Adapter : NVIDIA GeForce 7300 GT (Microsoft Corporation - WDDM) (8 PS3.0, 4 VS3.0 450MHz, 256MB DDR3 2x398MHz, PCIe 1.00 x16)
Graphics Processor
Storage Devices
WDC WD1600YS-01SHB0 (164.7GB, SATA300, 3.5", 7200rpm, NCQ, 16MB Cache) : 153GB (D:)
Seagate ST3320620AS (320GB, SATA150, 3.5", NCQ, 16MB Cache) : 298GB (E:)
Seagate ST3320620AS (320GB, SATA150, 3.5", NCQ, 16MB Cache) : 298GB (F:)
WDC WD3200AAJS-65RYA0 (320GB, SATA300, 3.5", 7200rpm, NCQ, 8MB Cache) : 298GB (C:)
LITE-ON DVDRW LH-18A1P (ATA66, DVD+-RW, CD-RW, 2MB Cache) : N/A (G:)
Logical Storage Devices
XP (D:) : 153GB (NTFS) @ WDC WD1600YS-01SHB0 (164.7GB, SATA300, 3.5", 7200rpm, NCQ, 16MB Cache)
Samples (E:) : 298GB (NTFS) @ Seagate ST3320620AS (320GB, SATA150, 3.5", NCQ, 16MB Cache)
Audio (F:) : 298GB (NTFS) @ Seagate ST3320620AS (320GB, SATA150, 3.5", NCQ, 16MB Cache)
windows 7 (C:) : 298GB (NTFS) @ WDC WD3200AAJS-65RYA0 (320GB, SATA300, 3.5", 7200rpm, NCQ, 8MB Cache)
Optical Drive (G:) : N/A @ LITE-ON DVDRW LH-18A1P (ATA66, DVD+-RW, CD-RW, 2MB Cache)
Peripherals
LPC Hub Controller 1 : Super Micro Computer 631xESB/6321ESB/3100 LPC Interface Controller
LPC Legacy Controller 1 : Winbond W83627HF/F/HG/G
Audio Device : Super Micro Computer Enterprise Southbridge AC'97 Audio
Serial Port(s) : 1
Parallel Port(s) : 1
Disk Controller : Super Micro Computer 631xESB/6321ESB/3100 Ultra ATA Storage Controller
Disk Controller : Super Micro Computer 631xESB/6321ESB/3100 Serial ATA Storage Controller
USB Controller 1 : Super Micro Computer 631xESB/6321ESB/3100 Chipset USB Universal Host Controller #1
USB Controller 2 : Super Micro Computer 631xESB/6321ESB/3100 Chipset USB Universal Host Controller #2
USB Controller 3 : Super Micro Computer 631xESB/6321ESB/3100 Chipset USB Universal Host Controller #3
USB Controller 4 : Super Micro Computer 631xESB/6321ESB/3100 Chipset USB Universal Host Controller #4
USB Controller 5 : Super Micro Computer 631xESB/6321ESB/3100 Chipset USB2 Enhanced Host Controller
FireWire/1394 Controller 1 : ADS Technologies TSB43AB23 1394a-2000 OHCI PHY/link-layer Controller
SMBus/i2c Controller 1 : Intel 5X00/7X00 XMB Ch 21-0 SMBus
SMBus/i2c Controller 2 : Intel 5X00/7X00 XMB Ch 21-1 SMBus
SMBus/i2c Controller 3 : Intel 5X00/7X00 XMB Ch 22-0 SMBus
SMBus/i2c Controller 4 : Intel 5X00/7X00 XMB Ch 22-1 SMBus
SMBus/i2c Controller 5 : Intel 801xx/63xx SMBus
SMBus/i2c Controller 6 : IPMI T0 Controller
Network Services
Network Adapter : Intel(R) PRO/1000 EB Network Connection with I/O Acceleration
Network Adapter : Intel(R) PRO/1000 EB Network Connection with I/O Acceleration #2 (Ethernet, 100Mbps)
Power Management
Mains (AC) Line Status : On-Line
Operating System
Windows System : Microsoft Windows 7 Ultimate 6.01.7600
Platform Compliance : x64
Windows Experience Index
Current System : 4.5

A few things come to mind ...

I would disable your 2nd Network device in the bios and/or device manager.  You only need one in that system.  

You're running what appears to be a 'server' level system.  Some drivers that one would use on normal DAW setups often don't work on Server level systems.  This is true of both sound and video drivers often.  So make sure you have good/solid drivers in there.

And, as Dave mentions, make sure your power supply is sufficient to handle all the internal devices.

John


I would add that the memory modules should be of the same brand and if at all possible the same batch. Many people think if the numbers match they should match. Unfortunately that is not always case. Plus you are running 64 bits with only 4 GB of memory. I would up that to 8 GB.

As said the power supply is vital. It needs to be of a high quality and with adequate power.  Further your graphic card has too little memory.


BTW you did a great job in listing your system .

recently I've had a major system crash because I mismatched memory when upgrading my memory.  unfortunately I did NOT match the parameters correctly even tho I thought I did.  my CAS Latency and my voltage were different from the memory which was already in the system. 
 
when I added the new mismatched memory, I had a catastrophic failure of windows boot record.  I allowed windows to try to repair itself and that was a mistake.  with the mismatched memory still in the system while trying to repair itself, windows ended up overwriting the boot system and I ended up with 0M file size of the MBR.  I'm not going to have to reinstall windows.
 
I am convinced this all happened because of mismatched memory causing windows to think the MBR was corrupt and when it tried to repair itself in the corrupt state, it caused the catastrophic failure.
 
lesson learned.  I will never mismatch memory again.  from now on I will ALWAYS use the exact same part number and manufacturer or I'll replace what I have so that I can use all the same PN from the same MFG in all slots.

+1 on mismatched memory. RAM being the same is very important. I mismatched some on a computer once, and it wouldn't even boot up as a result. Put the old memory back in, and presto, back to normal. I concur that Rice Krispy sounds are generally due to system resources running out. X1 on a Dual Core? Never in a million years on my projects. Of course, I desperately try to stay in 96 khz mode. My Quad 6650 (or whatever that number is) is now petering out on me. Every time I add another effect to a track, the crackling gets worse, to the point now that the whole system is virtually unusable. Having to upgrade my computer as we speak. And the crackling is like yours, happening with any plugin control adjustments, sometimes even moving the mouse around while the project is playing. It may be time to upgrade for you as well!--ugh.