Sounds like you might not have WinZip installed, which you'd need to unzip it. You can also get a free extractor over here which should resolve the issue:
http://www.download.com/FreeExtracto...ml?tag=lst-0-5
I also found that I needed to save the zip file to the hard drive in order to extract from it, since simply opening the file without saving it first won't work apparently. Also, be careful that you're downloading the version of the editor made to run on your particular operating system.
Edit: Just tried downloading the newest version, and it seems that you also need to download and extract some dll files to the same folder as the editor in order to get it to work. The dll files are available from the same page as the editor itself.
[ 12-05-2005, 12:21 PM: Message edited by: Sinteuil ]