Situation:
You want to know how to change the IRPStackSize for computers using Windows NT, 2000, XP, or 2003 operating systems.

Solution:
Changing the IRPStackSize is sometimes necessary to fix problems or for troubleshooting a problem that occurs when it is set too low. In most cases, you should not do this unless it is recommend by another Symantec knowledge base document or a Symantec technician.

IRPStackSize is a DWORD value that can be set or created in the registry and is usually set by the operating system or by the installation of a specific application. The way the value is handled depends on the operating system. Find your operating system, and follow the instructions:

• To change IRPStackSize for Windows NT 4.0
  The default value is 11 and the range is between 4 and 12. The application of Service Pack 5 or later set the minimum limit to 7.
  
  Use the following steps to verify, change, or add the Value name: IRPStackSize to troubleshoot a problem or as directed by Symantec Technical Support or a Symantec knowledge base document.
  

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  WARNING: Symantec technical support strongly recommends that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure you modify only the keys specified. Please see the document How to back up the Windows registry before proceeding.

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  1. Click Start > Run.
  2. Type regedit.exe and then click OK.
  3. Navigate to the following key:
     
     HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters
     
  4. Look for the IRPStackSize value. If the value does not exist, you must create it:
     1. Right-click in the right pane, point to New, and then click DWORD Value.
     2. Type IRPStackSize and then press Enter. Type the value exactly as shown; it is case-sensitive.
  5. In the right pane, double-click the IRPStackSize value to enter edit mode.
  6. Change the Base to decimal.
  7. In the Value Data box, type 11.
  8. Close the Registry Editor.
  9. Restart the computer.

• To change IRPStackSize for Windows 2000, XP, and 2003
  Windows dynamically adjusts this value. The IRPStackSize value is not created during the installation of Windows.
  
  Some programs set this value by default. This prevents Windows from correctly managing the value. In this case, remove the value completely and restart the computer.

References:
For more information about IRPStackSize, see these Microsoft Articles:

• Event ID 2506 Error Message When you Start Windows 2000 -- Q238316
• Server Service Configuration and Tuning - Q128167