Hey Fly, Just want to jump in here if you don't mind. I would strongly disagree with upgrading to the Later Versions of LW. They seem to be really Buggy. The 4.12.xx Versions are probably the Best and Most Stable ever.
On to Filtering....
What I have done that works really well is to go to Tools > Options > Filter > Keywords and then add these file extensions: .wma, .exe, .rar, .html, .com, .zip, .mov. Be sure to tick apply and O.K. There are a ton of fake and corrupt files with these extensions. I will only download mp3 files that are larger than 2000kb - 3000kb. Also make sure thay have a bitrate.
Here is more good advise given by (Sleepless)
The Keyword Filter
Add
.wma to the keyword filter along with words like
Sponsored,
Unlimited,
Afford and any other specific words that keep popping up in your results.
How to add words to the keyword filter Click Me More words to add for both audio and video Click Me I really suggest you read this !!! Autogenerated Spam results - Information Link Sponsored Results - Information Link Info about .wma files - Information Link (provided by Raaf)