It is possible.
1) free some partition space and make the new linux OS partitions. Rmemeber that you will need several MB at the beginning of the hard drive in order lilo to boot properly (usually not needed, but when making this kind of install it's recommended).
2) if it is running another linux... just create a chrooted environment for the installer and start it, then follow console installation as normal
3) If it's running another *nix you can install a RPM depackager and install all the rpms one by one in the new root
4) If it's running Widow$ you can install vmware and then install from the vmware interface.
5) You always can install from a live CD. Boot from the live CD, so it will have a running linux on the box with ssh and so, and then start the installer.
6) If you are running any *nix you can always make a clean installation on your own box and then just export it via NFS or something like to the box where you want to install, then just create the partitions and copy all to them.
7) Remember to configure and run lilo after you have finished.
8) Remember to configure the network after you have finished or your box will boot and will have no network
Of course, you always can make your own autoinstaller, so you can upload it to the box and in the next boot it will kill the current OS and will replace it with a fresh one. Making this is more complex, if you need some info on these kind of stuff just visit
www.freshmeat.net or
www.sourceforge.net I am shure there are several free versions.
Hope this will help you.