If you're asking to operate your desktop with your laptop monitor as it's monitor then you can't do that. Laptop video connections are output only. You might be able to use a TV you have as a monitor but not your laptop's monitor.
If you're just wanting to access files from your PC's hdd using you're laptop then that's easy. You can get an external enclosure for your PC's hdd that connects via USB or eSATA to your laptop.