I am using nokia n73 for the tutorial purpose
As this operation is a critical one and do it @ your own risk.Your datacable lose connection,low battery may can interupt your updating and may cause damage to your phone and data.So you must be very careful while doing this.So use a good data cable n charge your battery upto full level.
First Backup your phone using nokia pc suite ( It may be avilable with your phone's cd or download fron nokia website) or if you have a memory card with enough memory then u can backup within your card.Just follow the steps to backup to mmc
go to the Tools – Memory select Options – Backup phone memory take out the memory card from the phone
Now download Nokia Software updater .Now install it n run it
Now just follow the operations insisted by the updating tool n your phone is now get updated.
Now restore your phone again by using pc suite or (if backuped in mmc Tools – Memory select Options – Restore from card).
Now your phone is fully updated.Now check your software version by using
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