You don't need 2Gb of RAM to run STALKER. I run it with 1Gb and the minimum spec is 512Mb. RAM is a hardware component.

What you do need is enough hard drive space in which to install it, which you didn't when you installed STALKER. Make sure you have deleted enough porn (or whatever is filling your drive up) and uninstalled enough programs to leave room for STALKER. Uninstall your current partial installation of STALKER (if it will let you) and reinstall it.