Leopard can't search for ".exe" files

I used to use OS X tiger to weed out PC viruses from thumb drives by searching .exe, .dll files and thrashing them. Now, with Leopard, it doesn't seem to be able to do it. I've tried using filters but still it does not give any results. I had to remove the executable files manually. Anybody know why this is so.

OS X was the best anti virus application I had ever used and I don't want to lose it.

 

Yes I did and on two different computers. That's odd