How to check firmware

Hi there,
i heard that some Nokia 6600 experienced issues with lag on applications, i have lag every now and then most noticable if i play games as stuff on the screen si always moving. my friend has the same phone but no lag on any applications. One i do experience it with is a game called frozen bubble, any idea how i check my firmware and if its old how i update it... also if firmware is not the problem do you have any other suggestions?
Thx