Depending on which p2p app you're using you can filter many if not most of those dud files (spam) out. For example, I filter out .wmv, .jpg & .exe

You'll notice each search you do gives replicated results. These more often than not come from certain T1 sources. Filter out the above words & you should find they no longer show up in search results. Of course you can add/remove filters anytime as it suits you.