Arduino files are found in 3 locations: The installation folder, the sketchbook folder, and the Arduino15 folder. The installation folder should be removed when you uninstall but the other two folders remain so you will need to remove those also to get a completely clean install. The Arduino15 folder is located at: On Mac OS X: /Users/(username)/Library/Arduino15 On Windows: Arduino IDE 1.6.5r5 and previous: C:\Users\(username)\AppData\Roaming\Arduino15 Arduino IDE 1.6.6 and later: C:\Users\(username)\AppData\Local\Arduino15 On Linux: /home/(username)/.arduino15 (a.k.a. ~/.arduino15) If you delete this folder then you will need to reinstall any Boards you have installed using Boards Manager after you reinstall the Arduino IDE. The sketchbook folder location is set in File > Preferences if you have any sketches or libraries that you want to save in there then back them up before removing it.
In this I would like to share experience with a cheep SIM800L GSM module that I purchased from my local supplier. This is a very nice and useful module that supports GSM/GPRS using 2G spectrum. You can also make calls and send SMSs using either AT commands or using Adafruit FONA library. You can download the FONA library from github page. Connection is very simple and a basic sketch uses only TX , RX, and RST pin. This module is designed to power somewhere between 3.7 to 4.8 volts but I powered up with 5 Volts external supply. Initially I tried to give power from my Arduino UNO 5 Volt pin. It initialized, but soon I got to know that my SIM is not getting registered in network. A quick googling gives me the answer that I would need a external power source as Arduino 5 Volts pin does not have enough power so that SIM get registered. It consumes a good amount of current for network search and registration. Also I also connected my modules GND pin to Arduino GND pin