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I am trying to install .NET framework 4.0 under Windows 7 but am getting an error with code 1406.

I checked the logs:

MSI (C:\a002a771e38ece7cca\netfx_Core_x64.msi) Installation failed.  
Msi Log: Microsoft .NET Framework 4 Setup_20121229_020733440-MSI_netfx_Core_x64.msi.txt
Final Result: Installation failed with error code: (0x80070643),  
"Fatal error during installation. " (Elapsed time: 0 00:02:15).

It all started with a cleanup tool for removing .NET 4.5 since I was trying to get rid of a linker error that it might have caused. However, after cleaning it up, I couldn't run both VS2010 and VS2012. Then, I uninstalled both IDE's and tried to install VS2010. That failed since I couldn't install .NET 4.0.

I really feel helpless and don't want to reinstall the whole OS from scratch. So what should I do?

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Who knows what sort of mess that cleanup tool caused in your system's registry? That's why one should stay away from automated system/registry cleaners most of the time. What does the MSI Log say? See if this page helps. You can also try renaming the Windows\Microsoft.NET\assembly dir before attempting a reinstall of .NET 4.0 –  Karan Dec 29 '12 at 21:40
    
@Karan, Yes, that's absolutely true. Never again. However, I was lucky since I was able to reinstall VS2012, and it fixed .net 4.0 and 4.5, and then installed VS2010, now both are fine. –  bfaskiplar Dec 30 '12 at 11:48

2 Answers 2

  1. Delete the contents of C:\WINDOWS\Microsoft.NET\Framework but not the folder itself.
  2. If step1 did not work, follow This guide.

Credits: http://blogs.msdn.com

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I had this problem on Windows 7 Ultimate N x64, when I was installing a Framework 4.0 security update.

For me, the root cause was that I did not have System.Xml.Serialization.xml in my Framework 4.0 folders, for whatever reason.

I had another Windows 7 x64 machine, so I copied the files from there: C:\Windows\Microsoft.NET\Framework\v4.0.30319\System.Xml.Serialization.dll and C:\Windows\Microsoft.NET\Framework64\v4.0.30319\System.Xml.Serialization.dll

(I think they're the same file, actually).

Reran it, and it worked like a charm.

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