Find a file in OS X Leopard? Spotlight not finding it...

I’m trying to find a file on my wife’s macbook that I know exists but can’t find it in spotlight. I’m pretty new to OS X so I’m not sure if there’s another utility that I can use to find this file (third party). Windows let’s you search in real time vs. Spotlight’s indexing service.. Is there a real-time search built into Leopard maybe?

I know the file exists because Mozy is backing it up… I just want to find it and delete it because it’s a dmg that I don’t need not to mention it’s 4+GB!