There are a number of things that we simply cannot promise and I will have that talk with them as well. I always try to put them at ease. I always ask for a chance to make things right when it all goes wrong. I run Belarc on the system and give it to them, before I start. I have had problems with people who accuse me of taking/replacing hardware. I do not need their parts, and will not stand for such an insult. I do understand the end user who has no clue about the system and what it does.
Kind of like driving a car without knowing how the engine works.