You will need to create an installation that includes both .NET 1.1 SP1 and .NET 1.1 SP1. First uninstall the .Net 1.1 software you have installed.
Create a new folder C:\DotNet (or choose another name)
Download into the folder Microsoft .NET Framework 1.1 Redistributable Package. The setup file should be saved as dotnetfx.exe.
Download into the folder Microsoft .NET Framework 1.1 Service Pack 1. Save the file as dotnetfxsp1.exe.
Open Command Prompt as Administrator
Change to the directory : cd C:\DotNet
Run the following commands clicking “Yes” when prompted :
dotnetfx.exe /c:"msiexec.exe /a netfx.msi TARGETDIR=C:\DotNet"
dotnetfxsp1.exe /Xp:C:\DotNet\netfxsp.msp
msiexec.exe /a c:\DotNet\netfx.msi /p c:\DotNet\netfxsp.msp
Run the installation program netfx.msi created by the above steps,
which contains the slipstreamed Service Pack 1.