INFO: Run, RunOnce, RunServices, RunServicesOnce and Startup (179365)


The information in this article applies to:

  • Microsoft Win32 Application Programming Interface (API), when used with:
    • the operating system: Microsoft Windows 95
    • the operating system: Microsoft Windows 98
    • the operating system: Microsoft Windows Millennium Edition
    • the operating system: Microsoft Windows NT 3.51
    • the operating system: Microsoft Windows NT 4.0
    • the operating system: Microsoft Windows 2000
    • the operating system: Microsoft Windows XP
This article was previously published under Q179365

SUMMARY

This article explains how the Run, RunOnce, RunServices, RunServicesOnce, and RunOnce\Setup registry keys relate to each other and to the Startup folder. It also describes the order in which these keys are loaded.

The information contained in this article supplements the following article in the Microsoft Knowledge Base:

137367 Definition of the RunOnce Keys in the Registry

Please see this article for an explanation of each of these keys.

MORE INFORMATION

Under Microsoft Windows 95, Windows 98, and Windows Millennium Edition (Me) where all keys are supported, the keys are loaded in the following order:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

<Logon Prompt>

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

StartUp Folder

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce

With the exception of the HKEY_LOCAL_MACHINE\...\RunOnce key, all keys and their entries are loaded asynchronously. Therefore, all entries in the RunServices and RunServicesOnce keys can potentially run at the same time.

Entries in the HKEY_LOCAL_MACHINE\...\RunOnce key are loaded synchronously in an undefined order.

Because the HKEY_LOCAL_MACHINE\...\RunOnce key is loaded synchronously, all of its entries must finish loading before the HKEY_LOCAL_MACHINE\...\Run, HKEY_CURRENT_USER\...\Run, HKEY_CURRENT_USER\...\RunOnce, and Startup Folder entries can be loaded.

The RunServicesOnce and RunServices keys are loaded before the user logs into Windows 95, Windows 98, and Windows Me. Because these two keys run asynchronously with the Logon dialog box, they can continue to run after the user has logged on. However, since HKEY_LOCAL_MACHINE\...\RunOnce must load synchronously, its entries will not begin loading until after the RunServicesOnce and RunServices keys have finished loading.

Because of different system configurations (such as a computer that is configured to automatically log on), any application that is dependant upon other applications that are executed under these keys having completed must be prepared to wait until these applications are complete. Other than this exception, the above description applies to Microsoft Windows NT 4.0, Windows 2000, and Windows XP.

NOTES:
  • The RunOnce keys are not supported by Windows NT 3.51.
  • The RunOnce keys are ignored under Windows 2000 and Windows XP in Safe Mode.

REFERENCES

For additional information on the RunOnceEx key, click the article number%2 below to view the article%2 in the Microsoft Knowledge Base:

232487 Description of RunOnceEx Registry Key

For additional information, please see the following article in the Microsoft Knowledge Base:

137367 Definition of the RunOnce Keys in the Registry

Modification Type:MinorLast Reviewed:9/27/2004
Keywords:kbinfo kbKernBase kbRegistry kbshell KB179365
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