Most likely this is spam and has some sort of malware (check the file on
http://virusscan.jotti.org/en and make sure you have an antivirus,
Avast has a free version for example). You can also click with the right button of your mouse on te file from within Shareaza and then check its bitprint on Bitzi (Web Services > See Bitzi ticket) ZIP archives are used a lot by spammers, installing
cyko's filter to rid of most them would be a good idea IMHO.