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Let us restore your computer to an earlier state.
Follow the instruction below to restore the operating system to an earlier time.
Click Start, type system restore in the Start Search box, and then click System Restore in the Programs list.
If you are prompted for an administrator password or confirmation, type your password, or click Continue.
In the System Restore dialog box, click Next.
In the list of restore points, click a restore point that was created at least one week before the current date, and then click Next.
Note: If you do not find a restore point that is at least one week old, select the earliest restore point that is available.
The computer restarts. The system files and settings are returned to the state that they were in when the restore point was created.
I would suggest you to run online virus scan on your computer.
If that does not work, let us perform System File Checker (SFC) scan which will help you in resolving the issue.
To determine whether the issue that you are experiencing is caused by one or more system files that are used by Windows Vista, run the System File Checker tool. The System File Checker tool scans system files and replaces incorrect versions of
the system files by using the correct versions.
Follow the instructions in the link below to run SFC scan.