The usual caveeats about network settings to connect the devices.
1.To export the N900 to your other device, you need x11vnc. Start it from the menu, it will start and close to run in the background. Connect to IP_OF_N900:5800 from your vnc viewer on your PC.
2. To get the screen of your PC, a VNC server has to run on the PC. You need a vnc viewer like PresenceVNC or vncviewer must be installed on the N900. Connect to IP_OF_PC:5800 .