Heaps of .exe, .zip & .rar files being shared are infected (some people would like to sabotage p2p by spreading infected files). Stay right away from those small files My best advice would be to avoid program files altogether...even those that are clean probably won't work anyway...will need a serial number/code to work.

If you do decide to download some of those formats, check the file with Bitzi before download.
How to use Bitzi

Make sure that your AV is kept updated & scan all downloaded files before you open them
WARNING: Viruses on network you should be aware of!