I'm more interested in why you think a long-defunct product bought 2nd-hand from someone in another country should carry a warranty.
As for supporting their product, that's another matter. I think they should have the proper documentation to help you out, but it's likely they don't. I think it's even more likely that nobody at that tech support center knows what a Central looks like. The fact that the tech thinks there's a reset button on the unit should be the tip-off. I'm not "in the know," but it seems to me like Rio is an empty shell of a company at the moment simply supporting the portable MP3 players they've most recently sold until their obligation to those customers is up.
Your best resource for help is here, obviously. However, there were so few Centrals sold that many of us here are in the dark when trying to figure out problems that haven't come up yet. The original designers do visit and post to this board, but many have moved-on from Rio and are working from their memory. Those who were at Rio until very recently may not have access to schematics and other technical data anymore to help. Unfortunately, this board is probably the best it's going to get as far as troubleshooting goes.
80GB 16MB MK2 090000736