Only second-generation Core CPUs with a TDP of 35W or less will work.

The i7-2540M is the fastest of these.  Make sure your system has a 90W adapter (integrated video) or 130W adapter (discrete video).

Hi,Can you explain further please when you say: Make sure your system has a 90W adapter (integrated video) or 130W adapter (discrete video).

I currently have a 65w adaptor/battery charger.

Do you know where I can find a list of compatible 2nd gen 35w processors for this specific laptop and if thats not possible could you tell me if the i5-3230m or i5-3320m are compatible?

cheers!

Those two are third-generation (the first digit indicates the generation) and won't work.

You'll be better off with a 90W adapter for the faster CPU.

I'll go with the i7-2640m then.

Can you tell me what you mean when you say integrated video and discrete video and how do I find out what I have?

Thanks,I have integrated intel HD3000.

Can you also tell me if I can put a 9 cell battery in instead of a 6 cell which is what I currently have?

I will buy a 90watt adapter when I go to upgrade.

thanks for all the help.

Thank you ,

last question : can I get a 130 watt adapter for quicker charging or should I only go for a 90 watt?

eg can they both be used with any latuitude e5420 battery?