From wikipedia:
Zwinky adds the MyWeb Searchbar to the following applications: Internet Explorer, Mozilla Firefox, Microsoft Outlook, Outlook Express, AOL 9.0 Email and Browser, Becky!, IncrediMail, MSN Dial-up Service, AOL Instant Messenger, Google Talk, ICQ, MSN Messenger, Yahoo! Messenger, and Windows Live Messenger.[1]
Once Zwinky is installed, the MyWeb Searchbar runs on startup. When users attempt to visit nonexistent pages, the software redirects them to search.mywebsearch.com. MyWeb Searchbar has been included on lists of known spyware.[2] A review from McAfee SiteAdvisor of the Zwinky website states, "In our tests, this site promoted downloads that some people consider adware, spyware or other potentially unwanted programs." There are also many user review complaints about the spyware that the Zwinky website supports.[3]