when i press shut down it doesn't turn off , but instead it restarts again.
Ans is so simple, you will have to Right click on My Computer, then Properties/Advanced Tab, and uncheck Automatically Restart under System Failure. This thing may resolve your issue although prior taking this action i would suggest you to run this command which is SFC\scannow. During scaning system will require operating disk. This procedure may take long time.
you will have to run sfc\scannow in your dos mode.