Thanks, appreciate your checking it out. Does indeed look like it's something unique to my setup.
I'm now certain IrfanView is not involved. I've just tried running from the XP Run box (Start > Run or [Win + R]). If PSP8 is initially not running and I enter something like this:
"C:\Program Files\Jasc Software Inc\Paint Shop Pro 8\Paint Shop Pro.exe" "C:\Docs\My Pictures\PHOTOS\Sorrento 2008\Test\20080413-105256.jpg"
then PSP8 duly opens and displays the file.
But if I then leave PSP8 open (with or without that file displayed) and repeat the run, with a new file, then I get the error sound and nothing else happens.
Same thing happens if no file is specified in the Run box, just the PSP8 executable.
It's as if PSP8 objects to being asked to run when it's already running.
I haven't got another PC at hand to try, but I'll do some PC spring cleaning and see if that helps.
Terry, East Grinstead, UK