Bought this from a friend, who did a restore to start me off clean.

I'm a newbie to the Mac World so bare with me.

I go to download Limewire, it pops up on the download manager and finishes downloading. Pops up on the desktop as a plain white document that I can't open or do anything with for that matter. I'm sure it's something I'm not doing right or something I don't know about. What do I need to do? The help is much appreciated in advance. Thanks!