Using Spotlight to search an external drive - normal fix not working..

Hi,

I have loads of SFX on an external drive and i would like to be able to search them from Spotlight. At first glance, it was an easy fix, go to Sys Pref, Spotlight and add the drive to the privacy tab..

Problem is, I used the drive as a back up of an older computer, so when I try to add it to the privacy list its says "drive is a Time Machine backup folder, You cannot add it to the privacy list''

So i thought maybe if I go onto Sys Pref, Time machine, and delete it from there it might help, but its not even there..

So question is, is there anyway of telling the OS, it can go into the privacy folder as it is isn't in fact being used as a time machine back up on this mac? Cant seem to get it to change the setting on the drive, even though on the desktop it just comes up as a standard drive..

Thanks!