Ron wants to know if LTE and GSM are the same. Leo says it isn't at all, and every carrier has made the move to LTE because it allows calls to be transmitted as data, while GSM is still radio-based. It's all data now.
What can he do with his old XP computer? The browsers aren't supported anymore. Leo says that if you can upgrade to Windows 10, that's the best option. But if not, put Linux on it! Leo recommends Manjaro or Ubuntu Linux. Download and put it on a USB Key, then reboot. See if you like it.