I am having problems with photoshop cs4 not rocognising all my ram in the options tab.
I have 4GB ram on a 32bit os which is recognised by the computer but cs4 has maximum available ram showing as 2GB.
You can't have an application recognize more than 2GB of RAM on a Windows 32-bit system. Details here. (Strictly speaking, 3GB is possible under certain circumstances, but highly unlikely that a program is compiled with this option.)
Solution - use a 64-bit OS and a 64-bit application.