Windows 7 / Getting Started

Control Sets

The Windows Boot Loader reads control set information from the registry key HKEY_LOCAL_MACHINE\SYSTEM, which is stored in the file %SystemRoot%\System32 \Config\System, so that the kernel can determine which device drivers need to be loaded during startup. Typically, several control sets exist, with the actual number depending on how often system configuration settings change.

The HKEY_LOCAL_MACHINE\SYSTEM subkeys used during startup are:

  • \CurrentControlSet, a pointer to a ControlSetxxx subkey (where xxx represents a control set number, such as 001) designated in the \Select\Current value.
  • \Select, which contains the following entries:
    • Default Points to the control set number (for example, 001=ControlSet001) that the system has specified for use at the next startup. If no error or manual invocation of the LastKnownGood startup option occurs, this control set number is designated as the value of the Default, Current, and LastKnownGood entries (assuming that a user is able to log on successfully).
    • Current Points to the last control set that was used to start the system.
    • Failed Points to a control set that did not start Windows Vista successfully. This value is updated when the LastKnownGood option is used to start the system.
    • LastKnownGood Points to the control set that was used during the last user session. When a user logs on, the LastKnownGood control set is updated with configuration information from the previous user session.

The Windows Boot Loader uses the control set identified by the \Select\Default value unless you choose the Last Known Good Configuration from the Advanced Boot Options menu.

The kernel creates the registry key HKEY_LOCAL_MACHINE\HARDWARE, which contains the hardware data collected at system startup. Windows supports an extensive set of devices, with additional drivers not on the Windows operating system DVD provided by hardware manufacturers. Drivers are kernel-mode features required by devices to function within an operating system. Services are features that support operating system and application functions and act as network servers. Services can run in a different context than user applications and typically do not offer many user-configurable options.

For example, the Print Spooler service does not require a user to be logged on to run and functions independently of the user who is logged on to the system. Drivers generally communicate directly with hardware devices, whereas services usually communicate with hardware through drivers. Driver and service files are typically stored in the %SystemRoot% \System32 and %SystemRoot%\System32\Drivers folders and use .exe, .sys, or .dll file name extensions.

Drivers are also services. Therefore, during kernel initialization, the Windows Boot Loader and Ntoskrnl use the information stored in the HKEY_LOCAL_MACHINE\SYSTEM \CurrentControlSet\Services\Servicename registry subkeys to determine both the drivers and services to load. In the Servicename subkeys, the Start entry specifies when to start the service. For example, the Windows Boot Loader loads all drivers for which Start is 0, such as device drivers for hard disk controllers. After execution is transferred to the kernel, the kernel loads drivers and services for which Start is 1.

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In this tutorial:

  1. Configuring Startup and Troubleshooting Startup Issues
  2. What is New with Windows Startup
  3. Boot Configuration Data
  4. BCD Stores
  5. System Recovery
  6. Windows Boot Performance Diagnostics
  7. Understanding the Startup Process
  8. Power-on Self Test Phase
  9. Initial Startup Phase
  10. Initial Startup Phase for BIOS Computers
  11. Initial Startup Phase for EFI Computers
  12. Windows Boot Manager Phase
  13. Windows Boot Loader Phase
  14. Kernel Loading Phase
  15. Control Sets
  16. Values for the Start Registry Entry
  17. Value Descriptions for Type Entries
  18. Other Registry Entries in the Servicename Subkeys
  19. Session Manager
  20. Logon Phase
  21. Important Startup Files
  22. How to Configure Startup Settings
  23. How to Use the Startup And Recovery Dialog Box
  24. How to Use the System Configuration Tool
  25. How to Use BCDEdit
  26. How to Interpret BCDEdit Output
  27. How to Back Up and Restore Settings
  28. How to Change the Default Operating System Entry
  29. How to Change the Boot Menu Time-Out
  30. How to Change the Order of Boot Manager Menu Items
  31. How to Create an Entry for Another Operating System
  32. How to Remove a Boot Entry
  33. How to View and Update Global Debugger Settings
  34. How to Remove the Windows 7 Boot Loader
  35. How to Configure a User Account to Automatically Log On
  36. How to Disable the Windows Startup Sound
  37. How to Speed Up the Startup Process
  38. The Process of Troubleshooting Startup
  39. Startup Troubleshooting Before the Starting Windows Logo Appears
  40. How to Start the System Recovery Tools
  41. How to Run Startup Repair
  42. How to Use BootRec.exe
  43. How to Diagnose Hardware Problems
  44. How to Use System Restore
  45. How to Manually Repair the Boot Sector
  46. How to Manually Update the BCD Registry File
  47. How to Manually Replace Files
  48. How to Reinstall Windows
  49. Startup Troubleshooting After the Starting Windows Logo Appears
  50. How to Restore the Last Known Good Configuration
  51. How to Enable Boot Logging
  52. How to Start in Safe Mode
  53. How to Identify Failing Drivers and Services
  54. How to Analyze Startup Problems in Safe Mode
  55. Event Viewer (Eventvwr.msc)
  56. System Information
  57. Error Reporting Service
  58. How to Use Device Manager to View or Change Resources
  59. How to Analyze Boot Logs
  60. How to Roll Back Drivers
  61. How to Temporarily Disable a Service
  62. Troubleshooting Startup Problems After Logon
  63. How to Temporarily Disable Startup Applications and Processes
  64. How to Disable Startup Applications Using the Shift Key
  65. How to Disable Startup Programs Using the System Configuration Utility
  66. How to Disable Startup Applications Configured Using Group Policy or Logon Scripts
  67. How to Permanently Disable Startup Applications and Processes
  68. Manually Remove the Entry