The “minimum requirement” on Windows Server 2003 is 128 MB of RAM. But it will run fine on less. To do this there are two text files that need change in the installer.
Copy the install files to your hard drive, then in the I386 folder of the installer do the following:
In DOSNET.INF change:
MinimumMemory = 134217782
MinimumMemory = 67108864 (or less)
In TXTSETUP.SIF search for RequiredMemory and change it from:
RequiredMemory = 134217782
RequiredMemory = 67108864 (or less)
The DOSNET.INF will change the requirement for the GUI installer. Only changing this will allow you to install within another Windows installation, but the text installer will use the TXTSETUP.SIF to look for the RAM requirement.
Thanks to http://www.cyberhq.nl/win2003 for the tip on how to do it.