I've noticed both Keil uVision 4 and uVision 5 share the (for Windows) identical filename "UV4.exe"/"Uv4.exe". This results in Windows (7) Explorer being unable to choose for a specific version.
You have to rename the "UV4.exe" from uVision 5 to "UV5.EXE" and update the startmenu shortcut.
Gulp. Are you saying that Windows have suddenly stopped being able to specify a full path to an exe file? For a huge number of years, it has been possible to have multiple programs with the same name in the computer - and also possible to start them - as long as the same-named exe files have been stored in different directories.
The "open with" Window does not accept Uv4.exe (actually UV4) as replacement for UV4.exe (which is UV5).
Yes you can both have and start them, but not though a .uvproj file. Since the full path isn't stored in registry of filetypes somehow.
The system path decides in which order the system looks for executable programs.
But even if the two exe files would have had different names (and remember that it's possible to rename or make copies of exe files) there is still an issue involved with associating file extensions with a program, when both uv4 and uv5 has project files with the same extension.