In Safe Mode run a full virus scan, Malwarebytes Anti-Malware free version
www.malwarebytes.org and SUPERAntiSpyware free
www.SUPERAntiSpyware.com . Remove any threats that they find. Then in Safe Mode, put your Windows 7 dvd in, click start, type command and right-click on Command Prompt, click on Run As Administartor and type in SFC /scannow and hit enter. After that runs open Computer, right-click on your C: drive, click on Properties, Tools, Check Now, click both boxes, click on Start, click on Yes and restart your pc and let Check Disk run.