unzipped files always open as .exe even though limewire states that the file I am downloading is a OS X file. I am using Stuffit expander to unzip is this the problem. Somebody help me please!!!!

No, stuffit is fine. The problem is those are Windows EXEcutable files (programs) that are misnamed.

Probably viruses or other malware: be glad they don't run on a mac.

Getting OSX apps via p2p networks is generally a bad idea. For free mac apps (and more), use your Apple Menu->Mac OSX Software link.

Program files should be larger than 2,000 KB (2 MB). Check the size of programs on your computer, as most will be 10 MB up to over 100 MB in size.