Cannot install several applications

In the last few days I encountered the same installation problem with three complete different applications. In all cases clicking setup.exe brought up the error message:
"The filename, directory name, or volume label syntax is incorrect"

As so often in every computer system: such error message doesn't help much. It is a riddle that only professionals can solve. Where o where is the WikiError that explains in simple words what all these mysterious messages mean - and what the user is supposed to do when he comes across them.

Since there isn't a WikiError:
What is the problem? What must I do?

In my case the three 'uninstallable' programs were:
Malware Byte's Antimalware (newly downloaded from their site)
Punch Home Design Suite (from their cd - earlier installed without a problem)
Recover My Files (newest version, earlier installed without a problem, also on other laptop)

I solved the problem myself - and hopefully the information helps others too.
Recently I had renamed the folder where I store all my software applications to: ● My Apps (to get it on top of the folder list). Apparently folder names with special characters confuse certain setup.exe files.
So I created a separate INSTALL FOLDER 'outside' my APPS folder, copy the desired setup.exe there, and delete it there after use. Problem gone.

Should I create the "outside" folder under Program Files or just on the C: drive?
Where do I need to create the folder?