Allright guys. I've got a MB MA700LL. Max ram per Apple is 2gb. Reports are three. I ordered 2-2gb sticks, tossed them in and tadaa! The "About this Mac" window says I've got 4gb installed. System profiler says 4gb installed. However, the iStat widget totals 3gb. Any ideas why there's a discrepancy?
The best way to know for sure if it's using the RAM (especially considering System Profiler recognizes it) is to open up the Activity Monitor, open up enough apps to use up that much memory (Firefox and Photoshop are great for this) and keep an eye on the system memory at the bottom to see if it's actually being allocated.
Yes. Inactive simply indicates that it is reserved, in case it needs to be used, but is not actively being used. According to the little pie chart at the right, your MacBook is indeed recognizing and using all 4 gigabytes of RAM.