Windows Checked Builds

I've noticed that some users have Checked builds of Windows, and that a certain BSOD named STOP 0x00000001: APC_INDEX_MISMATCH only appears on Checked builds of Windows operating systems.

From what I understand, Checked builds of Windows are used for Driver Developers to have more accessibility and detailed information when bugs occur in the drivers they are developing. I tend to like to think of it as, a VM for Driver Developers to test the compatibility and stability of their drivers with the Windows operating system.

A Checked build is commonly referred to as a Debugging build of Windows, whereas, the Retail versions - the versions most of us are currently running - are referred to as Free Builds.

Here are the key differences between the two builds as quoted from Microsoft:

"The free build (or retail build):

The free build of Microsoft Windows is used in production environments. The free build of the operating system is built with full compiler optimizations. When the free build discovers correctable problems, it continues to run.

The distribution media that contain the free build of the operating system do not have any special labels--in other words, the CD that contains the free build is labeled with the Windows version name, without any reference to the type of build. 

The checked build (or debug build):

The checked build of Microsoft Windows makes identifying and diagnosing operating-system-level problems easier.

The checked build differs from the free build in the following ways:

• Many compiler optimizations (such as stack frame elimination) are disabled in the checked build. This makes it easier to understand disassembled machine instructions, and therefore it is easier to trace the cause of problems in system software.
  
• The checked build enables a large number of debugging checks in the operating system code and system-provided drivers. This helps the checked build to identify internal inconsistencies and problems as soon as they occur.
  
• Distribution media that contain the checked build are clearly labeled as "Debug/Checked Build." The checked build distribution medium contains the checked version of the operating system, plus the checked versions of HALs, drivers, file systems, and even many user-mode components."

Please note, that Checked Builds are much larger and slower than their Free Build counterparts.

More Information - Checked Builds and Free Builds