I know there is a workflow to move documents from one folder (or a library) to a different one inside the SharePoint based on their approval status or version number etc. But I want to move the document to a local folder in a drive (say P:) instead of a folder inside the sharepoint site.
If you need this to happen in real time then you will need an event receiver. If a small delay is acceptable then you can go with either a custom workflow or a Timer Job.
Lastly, you could simply create a PowerShell script that has the logic you need and attach it to a Scheduled Task in Windows.