But be careful what you buy, even with memory from the same ‘kit’, the installed location and the size of the memory matters. HP has a .pdf showing optimal memory configurations: http://h20331.www2.hp.com/Hpsub/download....

In the introduction you should link fixers to this excellent doc: https://www.ifixit.com/Misc/HD_Software_...

It is really critical, super easy, and free(!) to clone your existing drive onto the new one you will install. I ran into one error, but SuperDuper! support replied immediately on how to fix it...Thanks ifixit and SuperDuper! (I ponied up the $28 for the software anyway, I was so impressed!)