Define "crashed" -- were you trying to flash a new ROM or recovery image on it? If you were, and something went haywire . . you're possible SOL if you're a Cellular South customer. If the phone's just acting wonky, you can reset it to factory defaults (Settings -> Privacy -> Factory Data Reset).
If you didn't try anything warranty-voiding on the phone, just take it back to the store and get them to replace it under warranty. Otherwise, there's different things you can try, but they have varying levels of success. Some folks have claimed they've been able to do full restores of a CellSouth Milestone -- but I haven't found a complete set of instructions on how they did it.
