temperamental icon and Avast
Thanks, but maybe our computers, systems or maybe AV software have different problems! My volume icon has disappeared and reappeared several times over the past 2 days, and I have just tried what you suggested above. The SplashLite and vlc programs close OK and the volume icon is still there. I have no problems with adjusting the volume with my icon, including when the players are running. I am having problems telling SplashLite to stop playing a video at the moment though. Sometimes it responds and sometimes it doesn't.
A few searches revealed that Avast allegedly (according to reps, who seem a little defensive and petulant sometimes) sometimes flags files as corrupted when it simply can't open them. Maybe it's a temporary problem with Avast, like when it kept identifying Microsoft files as suspect. I think it runs all the time in the background.
Thanks for the tip on opening Task Manager - previously the only way I knew how to do it was Ctrl-Alt-Del!