To remove Do Searches browser hijacker for free you may download a program called AdwCleaner (absolutely no-cost program for malware like Do Searches removal).
You will scan your PC with it and will get rid of this nasty hijacker.
Alternatively, you may follow this guide on how to remove this dosearches.com automatically - http://www.system-tips.net/remove-dosearches-com-browse...
However, don't buy the program recommended there. Simply install it and run. Then click "Tools" and "Reset browser settings". This is what I did when I had this problem with my Firefox... I just used this utility (which was free) and it helped me remove this nasty malware from my PC.