You describe a very common problem with (p-p) downloaded programs. Oftentimes there are missing files, corrupted installers, etc. That's the good news.

The bad news comes when the programs function exactly as the uploader planned: trashing or hijacking your computer, sending spam or copies of the rogue program from you to others via network or e-mail (which they'll open because it comes from you). You can end up with an obvious problem that can only be solved by purchasing software from the very people who gave you the malware, thus demanding a ransom for your computer!

There are also many who have a financial interest in discouraging p-p filesharing, by circulating malware. When it comes to sharing executable files it seems that they have won, as no one here would suggest that it is safe.

Check out the arcade on this site (see tab at top of page). They're not the fanciest games, but all are safe and we encourage friendly competition.