How about getting us the model and serial number from under the seat so we can see which mower you have. Most likely the drive belt for the hydrostats has broken or came off.
Hydro's may be serviceable but with knowing which drives you have we can't answer that. If the belt isn't the problem then we may need the model number off of the drives themselves. It would be unusual for both drives to stop at the same time due to failure. More likely belt issue.
