Knock, Knock. The Village Idiot has a question.

This system that I built will lock-up every time a really CPU intensive app is running. When running a HDD intensive app, no problems. Here are the stats for the various parts:
Memory: Geil Value Series 184 Pin 512MB DDR PC-3200
Manufacturer: Geil
Speed: DDR400(PC3200)
Type: 184 Pin DDR SDRAM
Error Checking: Non-ECC
Registered/Unbuffered: Unbuffered
Cas Latency: 2.5 6-3-3
Support Voltage: 2.55V-2.85V
Bandwidth: 3.2GB/s
Organization: 64M x 64 -Bit
Special Features: With Extreme Performance Heat
Spreader
Warranty: Lifetime

Mobo: BIOSTAR "M7NCG 400" nForce2 IGP Motherboard for AMD Socket A CPU -RETAIL
Supported CPU: Socket A AMD Athlon/Athlon XP/Duron
Processors
Chipset: NVIDIA nForce2 IGP + MCP
FSB: 200/266/333/400MHz
RAM: 3x DIMM support Dual Channel DDR333/266/200 Max
3GB
IDE: 2x UltraDMA 133 up to 4 Devices
Slots: 1x AGP 8X, 3x PCI, 1x CNR
Ports: 2xPS2,1xLPT,1xCOM,1xVGA,6xUSB2.0(Rear
2),1xLAN,1xGAME,Audio Ports
Onboard Audio: Realtek ALC650 6-Channel AC97 CODEC
Onboard Video: GeForce4 MX
Onboard LAN: Realtek 8201BL 10/100Mbps
Form Factor: Micro ATX

CPU: AMD Athlon XP 2500+ "Barton", 333 FSB, 512K Cache Processor - Retail
Model: AMD Athlon XP 2500+
Core: Barton
Operating Frequency: 1.83GHz
FSB: 333MHz
Cache: L1/64K+64K; L2/512K
Voltage: 1.65V
Process: 0.13Micron
Socket: Socket A
Multimedia Instruction: MMX, SSE, 3DNOW!, 3DNOW!+
Packaging: Retail Box (Heatsink and Fan included)

I used the stock Heatsink and Fan that came with the CPU since this system was built for a co-worker who is only doing e-mail and downloading his pictures from his different digital cameras. He is using the built-in video since he wanted to save money. There is a fan in the side of the case which is
pointed at the CPU and the North Bridge blowing over both. The power source has two fan in it which are pulling out. I did have to raise the votage to get the CPU running at the proper MHz (166), which before I raised the FSB and Voltage, would only run at 133Mhz. I did apply the newest BIOS before I raised the FSB and it did not seem to help the CPU recognition. Any ideas that don't include spending more money would be great. I have also updated all drivers and have all windows updates. This system is running
Windows XP Home SP1a fresh install.

Thanks Everyone for your time and help!!!

Reseat the heatsink, ensure that any film which was over the thermal pad on the base of the stock heatsink had been removed.

What volate is the CPU running at? 1.65?

I need to get over to his place to do the work, but the plastic was removed and yes the Volts are at 1.65. Does this sound like a heat issue or maybe the power source (don't think it would be the power source since the CPU is the only problem).

what kind of power supply do you have? That would be the first thing i would check in your situation.

Why did you get 3200 Memory If your not OCing your CPU

I got him PC3200 since it is running about (if not a little higher than) the FSB on the CPU. I am rather sure I had him get a Sparkle and I know that the power supply that came with the case suprised me because it seemed like a good brand; unfortunatly I can't remember the names.