SWI-Prolog depends on the MSVC runtime library, currently VC90.CRT. This library is not shipped with the installer. By default, the installer tries to detect whether the runtime is available and installs it from Microsoft if it cannot be detected. There are two possible issues with this:
- On some systems the automatic install fails, e.g., because the machine is not attached to the network, uses a proxy, etc. In that case, install the runtime `somehow' by hand and retry installing SWI-Prolog.
- On some systems, notably those where Windows is not installed
in the default
C:\windowsfolder, detection fails. Make sure that the runtime is installed and uncheck the tickbox Install VC runtimes in the installer.