Does the iFP790 have a mains charger?

Yes, there is likely a main fuse in your 2009 Kymco Venox 250 motorcycle that could have blown if you connected the charger directly to the + and - terminals on the starter. Many motorcycles have a main fuse located close to the battery or the fuse box to protect the electrical system from overloads and short circuits.
When you connect a charger directly to the starter terminals or other critical electrical components, you risk damaging the electrical system and causing a short circuit. If there was a surge of current due to improper connection, it could have blown the main fuse to protect the rest of the electrical components on the bike.
To troubleshoot the issue and restore power to your motorcycle, follow these steps:

1. Locate the Main Fuse: Check your motorcycle's manual or service documentation to find the location of the main fuse. It is often located close to the battery or in the fuse box.
2. Inspect the Main Fuse: Remove the main fuse and visually inspect it. If the main fuse is blown, you will see a break in the metal strip inside the fuse. Replace the blown fuse with a new one of the same amperage rating.
3. Check Other Fuses: Even though you mentioned that all the fuses are good, double-check all the other fuses in the fuse box to ensure none of them have blown.
4. Check Battery Voltage: After replacing the main fuse, check the voltage of the battery using a multimeter. Ensure the battery has enough charge (around 12.6 volts or higher) to power the electrical components.
5. Reconnect Charger Properly: If the battery voltage is low, connect the charger properly to the battery terminals (positive to positive and negative to negative) and charge the battery until it reaches an appropriate level.
6. Recheck Power: Once the battery is charged and all fuses are confirmed to be good, turn the key on and check if the lights and gauges receive power.

If you have followed these steps and still do not have power to the motorcycle, there might be other electrical issues caused by the improper charger connection. In that case, it's recommended to seek the assistance of a qualified motorcycle mechanic or electrician to diagnose and fix the problem correctly.

THE CARS MAIN BATTERY IS DEAD.
WHAT IS THIS TENDER THING, A BATTERY CHARGERS/?
YES , HOW MANY AMPS IS THIS CHARGER?
MAIN BATTERY DEAD.
BATTERY LUGS LOOSE
BATTERY LUGS RUSTY, 2 CABLES 4 ENDS NOT RUSTY
OR BLEW UP HUGE FUSES./

TENDER MEANS? WHAT? NAME IT AND MODEL, FOR BEST ANSWERS AND IF WIRED BACKWARDS.

rear main seal, yes

Yes you can charge your satnav through your pc using the mini USB lead. It will take approx 8 hours to charge fully compared to 4 hours using a car charger or a mains charger.

The problem is your power supply charger, or the DC jack in the laptop, or bad battery. Remove the main battery and see if it will start up, if yes! the battery will need to be replaced, If no! plug charger in the computer and apply side-way pressure on the DC jack "not to hard" and press power repeatedly to see if you can start it, If yes! It is the DC jack that has broken free from the motherboard, If no! It is the power supply or motherboard. I suggest a computer tech

Yes you can charge the battery through the computer with the usb cable. However it will take twice as long, approx 8 hours, to charge as the car charger or mains charger which take approx 4 hours.

Yes it can be charge. You can see some options HERE

here is link download the updates

i cannot find my iriver ifp 790 mp3 player software.does anyone have a location to get one?

No, it will not be safe to use it again, and yes, the yellow liquid is VERY DANGEROUS. Please do not use it again, you need a new charger.
i dont think the batery was affected, but if it was, you also need to throw it way and get a new battery.