after formatting my iphone 3gs, (4.1 ios), would it have a maintained IOS or i vl need to install it again, simply i mean that if i format my iphone then ios 4.1 would need to be installed again or any oyher issues would arise ? please guide me about it !

Can you clarify your question? As you upgrade the iOS on your iPhone device, there is no additional steps required with regard to re-installing apps, or configuration.

JorgeM, i mean that lets suppose i formatted my iphone 3gs (ios 4.1), then after formatting, would my ios need to be reactivated again ? and what about apps etc ? apps would be still there after formatting ?

not upgrade, formatting

not upgrade, formatting

Ok, so I guess you what are referring to is restoring back to factory defaults...

When you have all sorts of issues with your iOS, you could invoke recovery mode to restore iPhone to default factory settings. this will restore the original state as when you first received the phone. The downside that all data and information stored on your phone will be lost. However, you could apply a restore from iTunes and that will bring back your data. I'd perform a backup before you invoke the recovery mode/restore.

You do have to reactivate after a clean, restore.

what software did i use for converting video to iPhone format?

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