
The Imagemagick download page helpfully suggests installing the Visual C++ 2010 Redistributable Package (x86) package if there are any problems. This, too turns out to fail with the same "not a Win32 application" error.
The box scans clean for viruses, other applications load and run as usual. Other freeware can be installed with no problems, no events logged to indicate a problem. Rebooting / reinstalling makes no difference.