4 GB Of RAM In Ubuntu 32bit [How-to]

Ubuntu 32bit only supports 3 GB of RAM so if you have 4, only 3 will be used. You can use the 64bit version for all 4GB of RAM memory to work, or follow the instructions in this post to make the 32bit version of Ubuntu to work with 4GB or RAM.

Firstly, please note that to achieve this, you must install the Ubuntu Server Kernel which has Phisical Extencion Address Enabled (PAE) enabled thus allowing Ubuntu to see all 4 GB of RAM.