This is a good time for my favorite rant again. You can and should backup your entire EQ directory to another hard drive, CD, DVD or even the same hard drive if thats the best you can do.
EQ does not have to be installed. You can restore from the backup, or copy onto a new hard drive and be ready to rock and roll.
I have never lost my eqclient.ini, but before reinstalling/repatching I would wait for another answer.