It sounds like you have a hijacker.
The first steps will be to have run the free spyware removal software Spybot - Search and Destroy and Ad-Aware. If there are problems after this step, we will continue with asking you to download Hijack This and post a HijackThis log. This log will enable us to understand what is happening on your system and potentially quickly spot and then rectify the problems you are having.
Download, install, update and run these two applications:
AdAware (get the free version which is named Adaware SE): http://www.lavasoftusa.com/software/adaware/
Spybot S&D: http://www.safer-networking.org/en/index.html
If these do not work completely I suggest you then post a HijackThis log for assistance with your problem.
Read the pinned post in the HijackThis forum, here Carefully read and follow all directions exactly.
Run a log, and post it in the HJT forum, at this link
. Do not attempt to fix anything, yet.
A member, of the HJT Team, will examine the log and offer assistance.
Please be patient. It may take a while to get a response because the members of the HJT Team are very busy. Please
, be patient, this team is manned by volunteers. They will help you as soon as possible
Once you have made the post, please DO NOT make another post in the HJT forum, until it has been responded to by a member of the HJT Team.
The first thing they look for, when looking for logs to reply to, is 0 replies
. If you make another post, it will show 1 reply
A team member, looking to see if a reply has been made might assume someone is already assisting you and will not respond.
So, just make your post and wait for a response until a team member responds.