is any of this three types a swap partition? You can check it with the command
or possibly hda instead of sda.
To list the partition table enter p. If you have a swap, it should say "Linux Swap / Solaris" at one partition. To quit enter q. You can also use any other partition utilities you like. Or take a look to the file /etc/fstab. If your system uses a swap, it should be listed in this file.
Regnum Online needs a lot of RAM. If you have 2 or less GB, it will happen more often that your computer freezes when you play or load Regnum, if you don't have a swap.
My system has 2 GB RAM and I experienced the same system crashs without swap, if I have also applications like Regnum+web browser+feedreader+gmplayer etc open.
Did someone else install your Linux or did you install it yourself?