Independent of your hardware configuration, you must edit data\settings.txt so the following line reads:
Maximum Number of Systems := ***
where *** is a integer not greater than 255.
Secondly, you must edit data\systemnames.txt so it has at least as many system names as the value you entered above. If you look in the mods forum here, you'll find some custom systemname files that people have already modded.
If you're getting an out of memory error due to a hardware problem or for some other reason, I can't help you. Maybe someone else will chime in.
Hope this helps and yep, it is a great game.
[This message has been edited by s_rat (edited 03 February 2001).]