I at last decided to buy a 2GB SO-DIMM to install on my old EEEPC 900. The installation process has been quite simple just matter of unscrewing the rear cover, unplugging the old module and replacing it with the new one.
The EEEPC performances have been improved only marginally, at least during everyday uses. By the way the upgrade did cost me only 25€.
So this short post is mostly a reminder, to my readers and myself, that all test I'll do on the EEEPC since now will be with the upgraded 2GB RAM and not with the original EEEPC 900 configuration.