BSOD Errors - Non-Executable Command?

I just built my new system (specs below) and got it up and running today. It's blazing fast, the temperatures are acceptable, and no overclocking has been done yet. The RAM is installed in slots 2 and 4 and the boot SATA drive is on SATA1. I only have one data drive hooked up at this point in time, so two hard drives are going.

I am running a legit copy of Windows XP Professional.

During no particular trigger, Windows will give me a BSOD stating that there was an "attempt to execute non-executable memory" and crash the system. One of the memory ranges given was 0x000000FC (0xBA4CFB9C ...).

It doesn't happen on any specific loading of a program, service, or media.

Any idea where I could start?

Oh, also, I have four removable disk icons in My Computer, but I don't have a card reader installed, nor do I have USB flash drives plugged in. Any clue?

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DFI nF4 Ultra-D
Athlon X2 4400+ Dualcore
2GB Corsair XMS 400/3200
eVGA nVidia GeForce 7800GT PCIe
nVidia GeForce 5400FX PCI
74GB WD Raptor SATA 10000 RPM (OS/Programs)
2x 250GB Samsung SATA 7200 RPM (Data)
480W Enermax Noisetaker PSU
Dell 2405FPW - Main
2x Dell 2001FP - Secondary/Tertiary
Logitech X-530's