I am running Windows XP Home Edition SP2 on a Pentium 4 machine.
Often, when exiting Avernum 4, I will press (alt-F4) instead of going to the Game Menu and clicking Quit from there. If I don't quit the game from the Game Menu, there is still a process running when I bring up the Task Manager. In fact there is a process left running every time I exit the game using (alt-F4)
It doesn't seem to adversely effect the program, but it does occupy a portion of memory. If I don't reboot my computer, I have to open the Task Manager and end each instance of the process manually.