I don't have error using CreateFile. But I can't read with ReadFile.
I had a reply on msdn forum http://social.msdn.microsoft.com/Forums/fr-FR/vcgeneral/thread/d19392c9-69f2-417d-a137-0a3e0d57751b
that tell me that ReadFile is not supported for LPT port. So I give up using windows API.
I give a last try using CParallelPort class from http://www.naughter.com/parallelport.html
and if I can't communicate with my PCI/parallel card I would have to find another way to acquire the footswitch signal.
I will let you know the results.