Help with a "troubled" employee.

I work in IT for a state agency.
I have a problem with an employee who keeps trashing his system due to extreme paranoia from hackers (or so he claims).
The first time I re-imaged his laptop from things he had done to it previously, I return to catch him going in and trying to turn off services, and uninstall programs, etc.

He claims that he read somewhere that these services and programs are backdoors for hackers.
Went back to look at the history of trouble tickets he has had, there is a long list of password resets which he claims hackers went in and changed his passwords. No! I think he's a moron who cannot remember his passwords. Anyhow....

Now a month later, another call ticket is in with the claim that I somehow didn't image his system correctly the last time.
This guy is going to be a big problem for me. In spite of us being a state agency, we are very customer oriented, "The customer is always right!" Even though I am being trashed by this guy, my management takes a very cavalier attitude towards our clients haranguing us and will not rock the boat, i.e., side with this loon.

I don't deserve to suffer this idiot and his personality disorder... I'm over a barrel here and I need to somehow reach this guy before it costs me my career. I have an appointment with him tomorrow, and I am so dreading it. I fear that I am going to blow up on the guy.

Please, any advice?