You may need to use Clean Installer to scan your downloads folder so that you can find it, because like they said above you may have a duplicate of it. Most of the times I've found the duplicates they had a hexdecimal name rather than the actual name of the file.

There's only one way -- the same as with any other custom content you want to remove from the game.

Take the file out of your My Documents--EA Games--The Sims 2--Downloads folder.

If it still shows up in the game after that, then you have a duplicate(s) of the file and must take that/those out of that same folder. Or you may have inadvertantly put the Insimenator file into another game folder (where it doesn't belong in any circumstance) -- should that be the case, remove it from there.

What exactly have you removed?