Start fresh and install plugins from an old install
The idea here is that you want to keep your old install intact, download a new indigo package (http://download.eclipse.org/) and just adds the existing plugins to your install. With Indigo this is now made super easy!
Step 1: Download and unzip your Indigo install: http://download.eclipse.org
Step 2: Import your plug-ins from your previous install by doing File > Import > Install > From existing install, pick your old install, select the plug-ins and there you go! You can chose to go piece meal, or chose to pick several entries, in any event dependency analysis will be performed to check the validity of the install.
Step 3: Click next a couple times and patiently wait for the bytes to download to your machine. Then restart and enjoy!
from http://lenettoyeur-on-eclipse.blogspot.com/2011/06/from-helios-to-indigo-is-easy.html