See if your carrier offers a OTA (over the air) upgrade. If so, you can use this method completely bypassing the need for a computer.
If no OTA upgrade is available, your other option is to take your device to where you purchased it from and see if they can do it for you. In many cases, stores will assist with this if needed as it keeps customers happy. The best time to go in will be when there are no other customers in store or just a limited number.
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