How to fix delta-search.com redirect (virus) problem
You don't have to buy any antivirus to fix this problem. Even though it is a good idea to scan your system with AV software, still this particular Delta Search redirect problem can be fixed manually. And I don't think that manual fixing would damage your system. What I recommend is that you follow some manual steps and guidelines, like these http://remove-malwares.blogspot.com/2011/09/how-to-fix-google-redirect-problem.html
This should help you, I believe. Make sure that you remove all browser add-ons associated with Delta Search, even though this is probably not the only thing that you should do. Follow other manual steps, and the problem should be fixed.