If you read through the posts made so far you'll get an idea of what DoSearches does and doesn't do when it's installed. The question of how it gets on to a system is not addressed but my bet is that it comes bundled with a download - possibly a game.
The main cause of DoSearches.com being active in all browsers is that it modifies the browser links. I can't see much sign of it being a serious threat (major registry modifications, modifying the MBR) - not yet, anyway.
From the thread the two most useful repair tools seem to be Shortcut Cleaner
I suggest you try those two and follow up with a Malwarebytes full scan.
With apologies to Marius at BleepingComputer, who has been painstakingly guiding another user through the cleanup operation for the past week, for cherry-picking the bits that seem most likely to achieve a result.
Message was edited by: Hayton on 27/10/13 04:47:14 GMT