Have you scanned for both malware and adware yet? If not download, install, decline the trial, update and run a full scan with Malwarebytes | Free Anti-Malware & Internet Security Software
to check for serious infection first, followed by SUPERAntiSpyware - Downloads
to check for spy and adware.
Check Browser Add-Ons and Search, disable any but Flash. If you see strange entries uninstall them in Control Panel.
Other tips for optimizing and going over your system thoroughly in Troubleshooting Steps for Windows 7
Be sure to at least establish a Clean Boot and use the recommended AV for best performance.