Assuming the thing turns on but does not load, you can try doing a factory reset (will wipe all data off the phone and set it to like new), if that does not work you can try flashing a new ROM to it (search for the stock RAM for your service provider for that phone, flash it using a computer. Instructions should be online in the same place you can find the ROM if it's out there). You can also bring the phone in to a store and see if they can get it working.