Hello i try to install .Net 4.0 and become that error code. Ive tried http://support.microsoft.com/kb/976982 and tries the msiexec.exe /unreg fix but nothing helps: Here the Logs: Action: Performing Action on MSI at C:\Users\Fionas\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\netfx_Core_x64.msi <form action="" class="messages" id="messages"> Returning IDOK. INSTALLMESSAGE_ERROR [There is a problem with this Windows Installer package. Please refer to the setup log for more information. ] MSI (C:\Users\Fionas\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\netfx_Core_x64.msi) Installation failed. Msi Log: Microsoft .NET Framework 4 Setup_20120710_110205410-MSI_netfx_Core_x64.msi.txt PerformOperation returned 1603 (translates to HRESULT = 0x80070643) Action complete OnFailureBehavior for this item is to Rollback. Action: Performing actions on all Items Action complete Action complete Final Result: Installation failed with error code: (0x80070643), "Schwerwiegender Fehler bei der Installation. " (Elapsed time: 0 00:01:28). </form>

Following discussion might help .NET 4 Installation Failure: IDOK. INSTALLMESSAGE_ERROR [The Windows Installer Service could not be accessed: 0x80070643 http://social.technet.microsoft.com/Forums/en-US/winservergen/thread/c717d615-e238-4918-8f3c-889355a62b9bI do not represent the organisation I work for, all the opinions expressed here are my own. This posting is provided "AS IS" with no warranties or guarantees and confers no rights.