When trying to install .NET 4 on a Windows Server 2003 or pre Windows XP SP3 PC, you get the following installer error:
Microsoft .NET Framework 4 Setup
Setup has detected that this computer does not meet the requirements to complete this operation. The following blocking issues must be resolve before you can proceed.
You must install the 32-bit Windows Imaging Component (WIC) before you run Setup. Please visit the Microsoft Download Center to install WIC, and then rerun Setup.
This is because WIC is part of the OS post Windows XP SP3 / Windows Server 2003 and is a requirement for .NET 4. WIC is basically a codec for working with images. To fix the blocking issues and install .NET 4, download WIC from the link provided in the error and install it before rerunning the .NET installer.