Windows 7 / Getting Started

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Stop 0xA or IRQL_NOT_LESS_OR_EQUAL

The Stop 0xA message indicates that a kernel-mode process or driver attempted to access a memory location to which it did not have permission or at a kernel IRQL that was too high. A kernel-mode process can access only other processes that have an IRQL lower than or equal to its own. This Stop message is typically the result of faulty or incompatible hardware or software.

Interpreting the Message

This Stop message has four parameters:

1. Memory address that was improperly referenced
2. IRQL that was required to access the memory
3. Type of access (0x00 = read operation, 0x01 = write operation)
4. Address of the instruction that attempted to reference memory specified in parameter 1

If the last parameter is within the address range of a device driver used on your system, you can determine which device driver was running when the memory access occurred. You can typically determine the driver name by reading the line that begins with

**Address 0xZZZZZZZZ has base at <address>- <driver name>

If the third parameter is the same as the first parameter, a special condition exists in which a system worker routine-carried out by a worker thread to handle background tasks known as work items-returned at a higher IRQL. In that case, some of the four parameters take on new meanings:

1. Address of the worker routine
2. Kernel IRQL
3. Address of the worker routine
4. Address of the work item

Resolving the Problem

The following suggestions are specific to Stop 0xA errors. For additional troubleshooting suggestions that apply to all Stop errors, see the section titled "Stop Message Checklist" later in this tutorial.

• To resolve an error caused by a faulty device driver, system service, or basic input/output system (BIOS), follow these steps:
  1. Restart your computer.
  2. Press F8 at the character-based menu that displays the operating system choices.
  3. Select the Last Known Good Configuration option from the Windows Advanced Options menu. This option is most effective when only one driver or service is added at a time.
• To resolve an error caused by an incompatible device driver, system service, virus scanner, or backup tool, follow these steps:
  1. Check the System Log in Event Viewer for error messages that might identify the device or driver that caused the error.
  2. Try disabling memory caching of the BIOS.
  3. Run the hardware diagnostics supplied by the system manufacturer, especially the memory scanner. For details on these procedures, see the owner's manual for your computer.
  4. Make sure the latest Service Pack is installed.
  5. If your system has small computer system interface (SCSI) adapters, contact the adapter manufacturer to obtain updated Windows drivers. Try disabling sync negotiation in the SCSI BIOS, checking the cabling and the SCSI IDs of each device, and confirming proper termination.
  6. For integrated device electronics (IDE) devices, define the onboard IDE port as Primary only. Also, check each IDE device for the proper master/subordinate/stand-alone setting. Try removing all IDE devices except for hard disks.
• If you encounter a Stop 0xA message while upgrading to Windows 7, 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, contact the hardware manufacturer to obtain compatible updates.
• If the Stop error occurs when resuming from hibernation or suspend, read Knowledge Base articles 941492 at http://support.microsoft.com/kb/941492 and 945577 at http://support.microsoft.com/kb/945577.
• If the Stop error occurs when starting a mobile computer that has the lid closed, refer to Knowledge Base article 941507 at http://support.microsoft.com/kb/941507.