Quote Originally Posted by joudbren View Post
This 721 is not a standard Intel Atom based Netbook. The OP has clearly identified that it's an Athlon Neo based system and Acer's own specs on their website indicate that it can address 4GB DDR3 ram. To the OP, as previously mentioned, you can remove the hatch on the bottom and it should show the two empty slots if the CPU is in fact a K125. Your only limitation then is your OS. You'll still need a 64 bit OS to see and use all of the 4GB. Cheers!
Then Acer didn't follow the guidelines Microsoft set out for netbooks because it was limited to 2gb only in order to quality for Windows 7 Starter edition if OP does have Starter version installed by default. Sometimes the hardware is 32 bit and wouldn't address the 4GB either.