Due to feedback from customers, on June 21, 2010, the Microsoft Support Lifecycle Team (MSL) posted a notice, via the Microsoft Support Lifecycle Blog, stating that version 1.1 of the .NET Framework is not supported on Windows 7 and Windows Server 2008 R2. Click here to read the Blog announcement.

In order to address any remaining questions, the following information has been provided. Please let me know if you have any additional feedback.

Understanding the Lifecycle and Supportability

Below are the Support Lifecycle Dates for .NET 1.1

· Mainstream Support for the .NET Framework 1.1 ended on October 14th, 2008.

· Extended Support for the .NET Framework continues through October 8th, 2013. While support for .NET 1.1 issues is still available, non-security hotfix requests will require enrollment in the Extended Hotfix Support (EHS) program. Please note that security updates will still be provided through the end of support at no charge.

Different from Support Lifecycle Dates, “supportability” defines what software releases will be supported by Microsoft in combination with other software releases. Broadly speaking, supportability is determined by “System Requirements”.

As detailed by the Microsoft Download Center website, .NET 1.1 has the following System Requirements.

· Supported Operating Systems: Windows 2000; Windows Server 2003 Service Pack 1 for Itanium-based Systems; Windows Server 2003 x64 editions; Windows Server 2008 Datacenter; Windows Server 2008 Enterprise; Windows Server 2008 for Itanium-based Systems; Windows Server 2008 Standard; Windows Vista Business; Windows Vista Enterprise; Windows Vista Home Basic; Windows Vista Home Premium; Windows Vista Starter; Windows Vista Ultimate; Windows XP; Windows XP Professional x64 Edition

· Microsoft Windows NT 4.0 requires Service Pack 6a.

Based on this information, .NET 1.1 does not meet the system requirements for Windows 7 or Windows Server 2008 R2. For this reason, .NET 1.1 is not supported on Windows 7 and Windows Server 2008 R2.

The decision not to provide support is based on changes in the Windows 7 and Server 2008 R2 Operating Systems that will not allow .NET 1.1 to be supported on these platforms.

The Microsoft .NET Framework 2.0 builds on the success of the Microsoft .NET Framework 1.0 and 1.1 to provide the best runtime environment for Web and Microsoft Windows client applications.

Microsoft’s compatibility goal for .NET Framework 1.1 applications is that they should work smoothly on the .NET Framework 2.0 except for a set of documented changes as provided here.

In addition, Microsoft recently announced that later versions of the .NET Framework (specifically .NET 3.5 SP1 and later) are now considered Components of the Windows OS. Customers can now be certain of support for the .NET Framework provided they are using a supported release of Windows.

The following links detail compatibility issues, testing scenarios, and other information related to .NET 1.1 compatibility. I hope you find these useful.

Microsoft .NET Framework 1.1 and 2.0 Compatibility


Compatibility Testing Scenarios


List of Breaking Changes


Runtime Breaking Changes


Design-Time Breaking Changes


Application compatibility MSDN forum


Deploying Microsoft .NET Framework Version 3.0