@utunnels: The 1GB of RAM is probably your problem. These days that's not very much.
@Providence: You press F5, or F6, or F7, or F8, to save when you reach a save point. Each key corresponds to a different save slot. That's what "Press F5-F8 to save" means. Once you've saved you can load from the associated save file (F5 saves to slot 1, F6 to slot 2, etc.).