Hiyas i am having a bit of a problem i brought the computer with 9gb of memory in it. So today i got another 1gb strip of memory to make it up to 10gb of ram. But the problem is i got 8 gb on the top shelf witch has 4 2gb strips of ram in it. And the bottom shelf as 2 512 strips of ram in it. I moved the 2 512s down a slot and put my new 1gb strip at the top and then i booted up my mac pro then went to system info and it coming back as 8gb. But there is 10gb in the computer so i thought i just put the new 1gb in on it self and it work fine then i put the 1gb on it own on the bottom self and the computer did not start up so i put the 1gb back to the top shelf and it worked again so then i thought i put the 2 512s in with the new 1gb then it can back and said i only had 1.5gb in the mac pro so then i tryed moving the shlf to the bottom slot and then it didn't boot so i thought i put it all back to as it was and it cam back with 9gb again so i thought i put the new 1gb strip into the computer again and see if it works then i came back as only showing 8gb again so im really confused i got the memory from ebay heres the link it was brand new http://cgi.ebay.co.uk/ws/eBayISAPI....582766&ssPageName=STRK:MEWNX:IT#ht_536wt_1139 the part number of the ram is CT12872AF667 please get back to me it wold be very helpful thanks loonboy