Howdy, I successfully installed Elyssa XFCE on an old laptop with 256Mb of memory, using a method I found in another forum, thought I'd post it here as well:
Boot up using a live CD that requires less memory (I had Xubuntu alternate lying around) and use Gparted to create a linux swap partition, remove all the others. Then you can boot up with Mint Live CD and the system can use the swap during boot and installation. I used guided partitioning and let it use largest available free space- the only downside is that it will create another swap partition.
Hope this helps, and good luck with your installs