I have tried to increase the RAM on an old netbook from Acer, an Aspire One ZG5. I went on www.crucial.com and using their built-in tool, I ordered the putatively correct module for my netbook, and I chose a 1Gb 200-Pin DDR2 SODIMM 128Mx64, PC2-5300. I followed step-by-step instructions here: http://www.ifixit.com/Guide/Acer+Aspire+One+ZG5+RAM+Replacement/3781
and everything seemed to work fine.
However, booting the netbook again it became evident that the system would not recognize all the RAM that I had installed, and the BIOS itself reported only 512Mb, not quite 1Gb that I purchased. Looking into this matter further, I think I understood that the Aspire One ZG5 netbook has an additional RAM module, soldered on the motherboard, providing 512 Mb of RAM.
Provided that is true, the additional RAM module would be totally unseen. Frankly I do not think that Crucial.com provided the wrong DDR2 module. What tweaks would be still needed? The computer runs on Ubuntu 13.04, but that should not be a matter of trouble as the BIOS comes first.
Thank you for any fruitful suggestion, Massimo.