Check out the tips here for eliminating porn from results: Direct instructions to eliminate porn from results

You could also try using the Hostiles List

Have you tried using the Advanced Search? Click on the category button (next to the Search button) & you'll see a link to Advanced Search at the bottom of the menu. From there you can refine your searches a bit.

You can also try removing the ultrapeers that you're connected to. If you're seeing heaps of spam, maybe you're connecting to bad UPs.
Tools > Advanced Tools & from there you can right click on an UP > remove.

And a couple more links that might help...
Problems with the search

How to find music (info for video, too)

Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see)