How to remove Snap.Do. Uninstall it as you would any piece of software to start with:
Control panel > Remove/Uninstall programs > Select Snap.Do from the list and remove....
You then need to set your browser homepage, default search engines and so on. You can see how to do that here:
http://malwaretips.com/blogs/snap-do-toolbar-removal/
I would suggest leaving the registry part of that guide alone.
Next, scan with Malwarebytes and, once you're remvoed anything dodgy with that, run a scan with microsoft security essentials.