You knew it would happen. If they're not ready to pay for emergency service, then forget about them. One reason to be hard-nosed about this is that getting your people out to fix computer problems isn't going to be cheap or easy. You most certainly have everyone on staff who can boot Windows already lined up to work on New Year's Eve.
People can be the hardiest.
We know of at least one integrator that has been flying people, at the company's expense, from Texas to Maryland just to test out and repair systems. It's been worth it. Without the personnel, they wouldn't stand a chance of fixing up their customers' problems. By this time, Y2K expertise shouldn't be a problem. But if you don't have enough Y2K experienced staffers, you can accomplish basic testing if your people are computer savvy and are equipped with the right tools.