It's really easy to write a program that causes W98SE problems. I have some own-written programs (in Visual Basic) running on my W98SE machine that all contain a similar routine, called when you select Quit from a main working screen, which closes the database and exits the progam. Well, you would have one, wouldn't you? Except that I've found the hard way that writing it straight, without checks, can leave you with a ghost version of the program running in background.
W98SE also creates its own problems by leaving memory management to the program rather than controlling it from the operating system, thus allowing progressive memory leaks. Adobe Exchnage, I've discovered, is a seriously bad offender here. Use that a few times and you quickly run out of memory.