Uninstall google chrome, and do a System Restore to a date prior to the start of the problem, and then download Chrome again and see what happens.
It sounds like a browser hi-jack, and the problem could be tricky to resolve if the relevant code has been embedded in your operating system's registry - a System Restore might take you back to a clean record of the registry at an earlier date.
If not, and if the various cleaners don't work (Ad-Aware, Spybot, Housecall, etc) then you will need to get a security tech to look through the registry and remove the offending code. Such code is often disguised and so needs someone who is savvy in spotting it as alien and additional to the needs of the system. If essential code is removed by mistake, the system can become inoperable, so you will need to make back-ups of anything you want to keep.
Tech-Support-Forum have some good security techs - they work for free, and so there is usually a queue and a wait of 24 hours or so.