I assume that you are using the openSUSE 11.1 DVD to attempt to install.
SUSE may want more RAM to be present before it proceeds. I suggest you google for SUSE installation, low RAM, as I am ignorant of any cheat codes you could use to allow SUSE to bypass the minimum of 512MB RAM it expects. There are these for an idea of how to proceed, but the methods may not work with 11.1
In any case you should choose one of the very light desktops, as I don't think that either Gnome or KDE will work with so little memory.