Sometimes installing a program or driver can make Windows run slowly or unpredictably. System Restore can return your PC's system files and programs to a time when everything was working fine, potentially preventing hours of troubleshooting headaches. It won't affect your documents, pictures, or other data. Read more https://windows.microsoft.com/en-gb/windows7/products/features/system-restore
Type in 'system restore' in the start menu and click on System Restore.