Please help me to take a complete backup of all the messages & contacts from my Nokia E61i into my PC.
Also, help me with the complete flash of the Nokia E61i, it hangs every now & then & does not let me install any application even after there is enough memory in it.
Go to Nokia's website and download the Nokia Ovi Suite. This is the official Nokia Phone management program and can be used to backup your contact, messages, photos, picture etc from your phone to your computer.
As for the flash. Use Nokia Ovi Suite again to find an update for your phones firmware. Follow the steps and it will automatically download and install the correct firmware to your phone.