|From Acer website|
* Single-channel DDR2 SDRAM support with one soDIMM module (for model with Intel® Atom™ processor N450 only) Up to 1 GB of DDR2 system memory (for Windows® 7 Starter for small notebook PCs) Up to 2 GB of DDR2 system memory (for other operating systems)
From my reading of this you cannot add an extra stick of ram. If your system has only 1gb you may be able to replace it with a suitable 2gb sodimm module.
Goin' Fishin' (Some day)