Hello Onoff - not sure if this is still of any help to you...
Best to look at the contents of the whole disk to see whats on there - perhaps the files have been ZIPped/archived.
I believe the reference you gave actually relates to programming HMIs via Vijeo Designer - totally separate software package.
Twido programming means creating a project within TwidoSuite - if you are making a project from scratch you provide a project name.
This creates a file... *projectname*.xpr
and also an associated folder called *projectname*
Within the folder are all the associated files of the project, using various extensions... .xml .xdm .tat .bmp
But it's the .xpr file you're after.
When trying to open an existing project be sure to spot the 'Format' option button as this selects what TwidoSuite looks for - and hides other files types from view.
TwidoSuite Project will show .xpr files
TwidoSuite Archive will show .xar files
TwidoSoft File will show .twd files
It's possible the project has been saved as an TwidoSuite Archive (.xar) in which case when it's opened it will create the .xpr file and associated folder.
If you haven't used TwidoSuite much then you might find it isn't too obvious that you've actually opened a project until you use the 'Project', 'Describe', 'Program', and 'Report' icons to navigate within the project/program.
Hopefully you've already cracked it!