when I got downloaded this game I got files with these really weird filenames. the problem was that the executable file needed to install the game had the name setup_the_witcher_enhanced_edition_1.5_(a)_(10712)_(g)[1] this meant the computer thought the file type was 5_(a)_(10712)_(g)[1] and not a .exe

changing the name to setup_the_witcher_enhanced_edition_1.5_(a)_(10712).exe seems to fix this

That's your browser (or whatever you downloaded with) fault. It should not have [1] at the end. That is a symptom of browsers that rename files that get broken/paused and restarted.

The proper names should be:

setup_the_witcher_enhanced_edition_1.5_(a)_(10712)_(g).exe
setup_the_witcher_enhanced_edition_1.5_(a)_(10712)_(g)-1.bin
setup_the_witcher_enhanced_edition_1.5_(a)_(10712)_(g)-2.bin
setup_the_witcher_enhanced_edition_1.5_(a)_(10712)_(g)-3.bin

sorry I forgot about this post, I already found a work-a-round to this issue by using gog galaxy. thanks for your help though