Go to Control Panel Add and Remove, and look for Incredimail listings and remove them.
Then download and run a simple registry editor... CCleaner, Reg Clean, Registry Cleaner, or AusLogics Registry editor... and remove any references.
Some of the Incredimail cartoons, animated software, and jokes can become infested with all sorts of evil stuff... so I would run a very good scanner, if you have one installed.
If not, I would download and install the free Grisoft AVG Antispyware, AntiVirus, and Root kit software. I would also run the free Adaware 2007, and SpyBot 1.4
If it comes back, run the cleaning software in both normal and safe mode.
If still there, download and run the HiJack This software free versions, then post the results here on a new thread for examination by the whizzes such as Momok, Howard_Hopkinso and others.. true experts in infestation removal.