resurrecting Old informix instant

I am really new to this informix and running IDS 7.3 on a SCO 5.4

we are having a ole informix instant which we did not used for a long time and and there is change request from one of our customer and forced to resurrect this instant.

On this machine there has been a hd failure and was replaced with a new one loosing root dbspace. I dont need to recover any of the databases but if some one can give me some help on host reinitialize (start from the beginning with out reinstalling) everything and start new would be appreciated

Thanks and Regads