I have an older Mac Pro (G5 Dual 1.8's)...The problem is I have four sticks of 512MB installed however when I look at "About This Mac" only two sticks show up in slots 1 and 2. I have all the same make/model of RAM and have even tried to move the sticks around into different slots, still same thing slot 1 and 2 are the only one's recognized. Slots 3 and 4 say they are "Empty" when in fact they are occupied with the same RAM as 1 and 2. ...I know this configuration is a little "light" for the Pro standards these days, but this is my file server and doesn't require a ton of overhead, I'd just like to get it running a bit faster, and instead of getting two 1GB sticks I'd like to figure out why the 2GB I have in there don't work. ...ideas?