It probably arrived as a semi-optional download with something else, always keep an eye open for these "extras". It's not a virus, trojan or worm but IS a nuisance and could cause malware to be downloaded at a later time. There is a good removal guide here: http://malwaretips.com/blogs/remove-conduit-search-virus/
After that I suggest running RootkitRemover, Stinger and Malwarebytes Free, all linked in the last link in my signature below.
To keep the latter free of charge do NOT accept the free trial.
Conduit is one of the worst offenders for producing hard-to-temove toolbars, and it produces them in bulk. That's what has turned this Israeli start-up into a billion-dollar company.
If you see one of these (Conduit Search) then you must assume there is other adware hiding on your system. The Microsoft forums offer a number of suggestions depending on the browser and version of Windows (see threads 1 , 2, 3 and 4) but the cleanup usually involves AdwCleaner and Malwarebytes.