Susie013164,

 

Consider the possibility that your system has been infected with some form of malware (malicious software).  There are a number of good applications which can search for and clean various types of adware, spyware, trojans and other malware.  These include SpyBot Search&Destroy from PepiMK software, AdAware from Lavasoft, RogueRemover from Malwarebytes and several others.  These programs can be downloaded for free from www.download.com, www.majorgeeks.com or several other sites. 

 

Download one (or all) of the mentioned programs, install them, update them and run them, one at a time.  Let them clean anything that they find.

 

Steve