I have just bought a Dell 640M which came with a 9 cell battery. Whilst great for the length of its charge, I had not realised that this battery was bulkier than the 6 cell. I would like to swap the 9 call for a new 6 cell battery (with possible small cash adjustment) if someone is interested in a swap the other way. I am not sure hwehter this battery will work on other Dell models (it is a Type UG679).
I have the Dell invoice to show how new the battery is and would expect to see similar proof of purchase for the swap.
Please reply to this thread or send me a PM if you are interested.