On a computer that has Microsoft .NET Framework 1.0, Microsoft .NET Framework 1.1, Microsoft Visual Studio .NET 2002 or Microsoft Visual Studio .NET 2003 installed, if you uninstall an update using Add/Remove Programs the file version may be rolled back to the last Service Pack.
This issue occurs because updates for the .NET Framework 1.0, for the .NET Framework 1.1, for Visual Studio .NET 2002, and for Visual Studio .NET 2003 were originally designed to work with Microsoft Windows Installer 2.0. The updates were not designed to work with Windows Installer 3.0. Windows Installer 3.0 is not supported on older operating systems, such as Microsoft Windows 95, Windows 98, and Windows Millennium Edition.
Windows Installer 2.0 has a limitation. It does not natively support the ability to remove an update. To work around this limitation, a custom remove functionality is built into the updates for the .NET Framework 1.0, for the .NET Framework 1.1, for Visual Studio .NET 2002, or for Visual Studio .NET 2003.