According to MS:

[qq]# Stop 0xA message might occur after installing a faulty device driver, system service, or firmware. If a Stop message lists a driver by name, disable, remove, or roll back the driver to correct the problem. If disabling or removing drivers resolves the issues, contact the manufacturer about a possible update. Using updated software is especially important for multimedia applications, antivirus scanners, and CD mastering tools.
# A Stop 0xA message might also be due to failing or defective hardware. If a Stop message points to a category of devices (video or disk adapters, for example), try removing or replacing the hardware to determine if it is causing the problem.
# If you encounter a Stop 0xA message while upgrading to Windows XP Professional, the problem might be due to an incompatible driver, system service, virus scanner, or backup. To avoid problems while upgrading, simplify your hardware configuration and remove all third-party device drivers and system services (including virus scanners) prior to running setup. After you have successfully installed Windows XP Professional, contact the hardware manufacturer to obtain compatible updates. For more information about simplifying your system for troubleshooting purposes, see " Troubleshooting Concepts and Strategies" and "Troubleshooting Startup" in this book.[/qq]

So basically, either faulty hardware, or faulty software. That really narrows it down. At least you know it's not the toaster doing it.