You have not provided enough information to answer the question except in the safest general terms, no it is not possible.
It will require some work before you do a re-install, create a backup of what you want/need from the current system first. Install the OS and during the installation process choose LVM. The manuals are very good for this, please review the Installation Guide and System Administration Guide;
http://www.redhat.com/docs/manuals/enterprise/
It's a good idea to have them handy, after all they are nice to have (get all of them).