Help picking the right statistical test?

Thanks for any help you can offer. I have a real-world problem where I'd like to find the right statistical test to solve the following type of problem. I can handle the math but I don't know what test to apply.

Suppose I have already run a study that shows a statistically significant relationship between the type of computer a person uses (PC, Mac, Other) and the brand of car he drives(Ford, Toyota, Honda, etc.). I can create a table showing the observed distribution of car brands out of 100 of each type of computer user -- for example, let's say of PC users, 35 drive Fords, 20 drive Toyota, 15 drive Honda, 15 GM, and so on.

Here's the question. Suppose I then have a new subject who drives a Toyota. What statistically valid analysis can I use to determine the probability he uses each computer type? For example so that I can categorically say that, based on my data, I can predict there is a 65% chance he's a PC user, a 55% chance he's a Mac user, and so on.

I'm also posting this in the Psychology section because I know how hard Psych majors get drilled in stats. Hoping someone can help.