Quoted from http://support.microsoft.com/kb/918685:

Error message when you install SQL Server 2005 or SQL Server 2008: "The file C:\Windows\Microsoft.NET\Framework\[version_number]\mscorlib.tlb could not be loaded"

Article ID: 918685 - Last Review: February 12, 2009 - Revision: 4.0

 

Error message when you install SQL Server 2005 or SQL Server 2008: "The file C:\Windows\Microsoft.NET\Framework\[version_number]\mscorlib.tlb could not be loaded"

 

SYMPTOMS When you install Microsoft SQL Server 2005 or Microsoft SQL Server 2008, you rec...

When you install Microsoft SQL Server 2005 or Microsoft SQL Server 2008, you receive the following error message: The file C:\Windows\Microsoft.NET\Framework\version_number\mscorlib.tlb could not be loaded. An attempt to repair this condition failed because the file could not be found. Please reinstall this program.Note version_number is a placeholder for the version number of the Microsoft .NET Framework, such as v1.0.3705, v1.1.4870, or v2.0.50727.

After you install SQL Server 2005 or SQL Server 2008, you may receive an error message that resembles this error message every time that you start Microsoft SQL Server Management Studio.

 

CAUSE This issue occurs because the path of the Mscorlib.tlb file is incorrectly inter...

This issue occurs because the path of the Mscorlib.tlb file is incorrectly interpreted during the Setup process.

 

WORKAROUND Important This section, method, or task contains steps that tell you how to modi...

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: 322756 (http://support.microsoft.com/kb/322756/ ) How to back up and restore the registry in Windows

 

For SQL Server 2005

To work around this problem, you must manually specify the correct path of the Mscorlib.tlb file in the registry. To do this, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\90\Tools\Shell\TlbAutoRepair\mscorlib.tlbNotes
   • If you install SQL Server 2005 on 64-bit operating systems, locate the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Microsoft SQL Server\90\Tools\Shell\TlbAutoRepair\mscorlib.tlb
   • If you install SQL Server 2005 Express Edition with Advanced Services, locate the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\90\Tools\ShellSEM\TlbAutoRepair\mscorlib.tlb
3. In the right pane, double-click the registry entry TlbPath. The Edit String dialog box appears.
4. In the Value data box, replace %CLRVERSION% with the following value: v2.0.50727Note The value v2.0.50727 indicates the version of the .NET Framework that the original release version of SQL Server 2005 uses.
5. Click OK, and then exit Registry Editor.

Important If you install a SQL Server 2005 service pack or hotfix, the service pack or hotfix will change the value that you replace in step 4 back to %CLRVERSION%. If the problem that is described in this article still exists after you install the service pack or the hotfix, you must following these steps again to work around this problem.

 

For SQL Server 2008

To work around this problem, you must manually specify the correct path of the Mscorlib.tlb file in the registry. To do this, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\100\Tools\Shell\TlbAutoRepair\mscorlib.tlb NotesIf you install the 32-bit version of SQL Server 2008 on 64-bit operating systems, locate the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Microsoft SQL Server\100\Tools\Shell\TlbAutoRepair\mscorlib.tlbIf you install SQL Server 2008 Express Edition with Advanced Services, locate the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\100\Tools\ShellSEM\TlbAutoRepair\mscorlib.tlb
3. In the right pane, double-click TlbPath.
4. In the Value data box, replace %CLRVERSION% with the following value: v2.0.50727 Note The value v2.0.50727 indicates the version of the .NET Framework that the original release version of SQL Server 2008 uses.
5. Click OK, and then exit Registry Editor.

Important If you install a SQL Server 2008 service pack or hotfix, the service pack or hotfix will change the value that you replace in step 4 back to %CLRVERSION%. If the problem that is described in this article still exists after you install the service pack or the hotfix, you must following these steps again to work around this problem.