Did you actually write a script and place it in init.d or could it be that you added a line to the end of rc.local?
In Mandrake (and others), these files would be located in /etc/rc.d/init.d/ and /etc/rc.d/rc.local, respectively. Also check /etc/bashrc and see if you're exporting it on boot.
If it's in your path then edit ~/.bash_profile and take it out.
Sorry I can't be more clear, but I'm not sure what you did, or what distribution you're using.