If you have a perfectly good working install of LC right now, do what I do:
COMPRESS AND BACKUP
Last Chaos installs to only one directly, the install isn't really an install so much as it is an unpack/directory process. If your LC is working just peachy keen and re-downloading and re patching is a pain, simply back it up on a memory stick, partition or backup drive. Unlike more current PC games which will install local files to different directories as well as patch in drivers (sometimes without your permission tsk tsk), this method is not reliable.