Sorry to be so dense but I'm not able to sort through all of the posts on this matter and come to a conclusion. I have an unmodified, just as it came in the box, Z61m running W7 Home Premium (that was an upgrade). I just want to max out the memory. How many modules at what GB can I install. Also, I'd like to use the best available as I plan to keep this laptop for a l-o-n-g time, so a brand recommendation would also be appreciated. I really appreciate your help.