There are lots of fake files around now, which won't play.
Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see)
Also, look up files with Bitzi before download: How to use Bitzi
If other users have rated the file, you'll see whether it's good or not.

Some crappy files are being deliberately shared by companies who want to sabotage p2p.
Fake files showing up in search results

And a bit more info below...
How to find music

* WARNING: Viruses on network you should be aware of ! *

You can use the junk filter (tools > options > filters > junk) to mark bad files as junk, over time LW will 'learn' which files are junk. It's not a perfect filter & sometimes you may get good files being marked as junk. for that reason, it's a good idea to have the filter set to display junk at the bottom search results... that way you can mark good files as not junk if necessary.

You can also use this hostiles list - it might cut down on the amount of spam that you see.
The TechNutopia Fullsize Hostiles List for BearShare and LimeWire