If you have a file (or better yet a link to a sweeps, or contest) that seems fishy, just hop on over to www.virustotal.com
select Scan a URL and paste and scan.
VirusTotal uses about 40 of the top virus scanners on the market, so you will know if a website or url is safe before you even go to it.
VirusTotal is a free service that analyzes suspicious files and URLs and facilitates the quick detection of viruses, worms, trojans, and all kinds of malware.
Happy Sweeping Everyone & Remember to keep your Cpu Safe. :)