For CS3 please see the system requirements listed at http://www.adobe.com/support/documentation/en/contribute/cs3/Adobe_Con tribute_CS3_Read_Me.pdf. It appears it requires at least 1 GB. I would double that for installing the software.
It appears to be the same requirement for CS4. I was finally able to locate some information at http://help.adobe.com/en_US/Contribute/5.0_Deploying/WS20B46D46-49B3-4 4f4-846F-8EB22B56A20B.html.
Europe, Middle East and Africa