welcome to the forum. it sound like you have been hit by something. download install, update and scan with malwarebytes antimalware and post the result here don’t forget to remove what it founds. might be asking for a reboot of the system if so do so.
http://www.filehippo.com/download_malwarebytes_anti_malware/
its a good first step
second do a scan with hijack this. and post the result here.
http://download.cnet.com/Trend-Micro-HijackThis/3000-8022_4-10227353.html
a good start you can do here to begin with.
good luck and let us know on the progress or, if you need more help.