A large proportion of my repair jobs are users reporting "My computer freezes." I ask, "does it freeze when you're doing something specific? - can it be reproduced?". They say, "No, it just freezes at any time."

How do you approach these types of "repairs"?

Often, with this type of vague problem description I can test the compuer for a while without ever seeing the problem. Then after making some changes or removing software, it's difficult to test and to be able to say you've fixed the problem.

Does anyone know of any good burn-in tests for these situations?