Plumbing question: sulfur smell in all sinks and showers of house?

Moving to a new house soon, and all faucets have water that smells strongly of rotten eggs or sulfur. What could be the source of the problem and how do I fix it?

I am going to get a plumber to help with this shortly, but I thought add ask for some fluther expert opinions first.

Note: The house has not been in use for about 6 months, I am guessing that this is partially, if not completely, to blame.

Thank you.