Yesterday was patch Tuesday, and Microsoft released security updates targeting a few products including the .NET Framework (see security bulletin MS07-040). This bulletin contains updates for the .NET Framework 1.0, 1.1, and 2.0.

The updates for the .NET Framework 1.0 and .NET Framework 1.1 are noteworthy because of a drawback both updates suffer from. Lets say you have an update for the .NET Framework installed and you then install a second update. Later on if you uninstall the second update, you would expect that your system would go back to the previous state i.e. update 2 is gone, update 1 is present. We think of this as a stack. You would be right if you were talking about the .NET Framework 2.0. But for the .NET Framework 1.0 or .NET Framework 1.1, when you uninstall the second update your system would not be reverted back to the first update, instead your would system would revert back to the last Service Pack. Once you are reverted back to the last SP, you would still not be able to easily install the first update.

This issue is caused due to the limitations in the installater technology used for these updates viz. Windows Installer (MSI) 2.0. KB939160 describes the issue and also provides a link to download a tool which will cleanup your system in case you need to uninstall the updates released for the security bulletin MS07-040. So if you plan on uninstalling these security updates for some reason, you should first take a look at KB939160.

Update on  11/9/2007 -

The issue described above affects updates for not just the .NET Framework 1.0 and .NET Framework 1.1, this also affects updates for Visual Studio .NET 2002 and Visual Studio .NET 2003. This problem is discussed more thoroughly in KB938244.

A new tool has been released that can be used to address this specific problem with any update for the Microsoft .NET Framework 1.0, the Microsoft .NET Framework 1.1, Microsoft Visual Studio .NET 2002 and Microsoft Visual Studio .NET 2003; more information about downloading and using this tool can be found in KB938244.

Note: The tool referenced in KB939160 may be used to address the issue only for MS07-040 unlike the new tool referenced in KB938244 which may be used to address the issue for any update for the previously mentioned products.