WARNING: Before perform the update, always perform phone backup! The author will NOT be held responsibility under any circumstances.
PRE-CHECK LIST
1. Make sure the phone battery is fully charged or connect to direct power source (recommended).
2. 'Wi-Fi' is connected to download the iOS 8 package.
3. Full iPhone 5 backup using iTunes. Follow this guide to install iTunes; http://emanduel.blogspot.com/2012/07/install-itunes-on-windows-xp-pro-sp3.html.
4. Once backup completed, disconnect the phone.
1. To view installed version:
Settings > General > About. Look for Version: 6.1.4 (10B350)
2. Settings > General > Software Update
3. Click Install Now
4. Terms and Conditions > Agree > Agree
5. iPhone will restart. Update in progress
6. slide to upgrade
7. Enter Passcode
8. slide to set up
9. Enter Passcode
10. SIM Locked > Unlock
11. Update Completed > Continue
12. Location Services > Disable Location Services > OK
13. Enter Apple ID password > Next
14. Find My iPhone > Use Find My iPhone
15. Welcome to iPhone > Get Started