Yeah you gotta go to
http://www.onmac.com and look at the "How To" section, then follow the instructions again, only the part regarding putting the XOM file in your home directory and blessing it via terminal, you will need to complete only that short section of the install, as when you re-installed OS X it would've changed preferences and not called upon this file at boot-up. The partition and all files are still on your drive, this just needs to be completed because it is the file that gives you the option of booting a different OS at startup.
Hope that helps.