we know the different types of DDR, that various versions of DDR don't mix and also that we can't use any DIMM's lying around the house and/or office (should you have any) in our laptop. Next we need to conclude just what type of i7 intel laptop DDR memory we need, specifically what will work in our laptop.

A good indicator what type is right for you is your laptop's age. Laptops produced in the years 2001-2003 will be very likely be DDR based. Laptops produced in the years 2004-2007 will be DDR2 and finally, laptop made since 2008 will be DDR3 (though some use DDR2). Armed with this information you'll know whether to buy a DDR SODIMM, DDR2 SODIMM or maybe a DDR3 SODIMM.

A second aspect you need to evaluate is the memory controller within your laptop. A simple method to find this out (and be told what type of DDR is right for us) is to run some diagnostics software on our machine. The truth be told, there are tens and tens of alternative ways to approach this. We recommend downloading and running CPU-Z, it's entirely free - download CPU-Z here.