If you're using LW 5, searching programs is disabled by default - because so many program files are infected & so lots of people end up with an infected computer. Please read the links below before even thinking about downloading programs.
Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see)

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

Fake files showing up in search results

If you really do want to download programs, go tools > options > security. Now you'll see an Unsafe Categories section. You can click on the Configure button to change what kinds of files you can search for. Click ok to save the change & click ok again on the main options page.

Be very careful with what you choose to download. Because it won't be LW's fault if you get infected, it will be your own
Make sure that you're using a good AV program. Keep it updated & use it to scan every file that you download, before you open the file.
Lime Wire » About Using P2P Software Safely

Lots of programs that you download won't work anyway, even if they're clean - they'll need a license/registration key.