You put a lot into a sim and you're going to want more than a 17 inch view shared between the outside view and the panel. At a minimum you'll want to display the panel separately, assuming you haven't built an awesome physical panel replica. An even if you have, wouldn't it be nice if you could simultaneously display left and right views along with the forward view?
One of the more simple approaches you can take is to use the capability built into windows. Windows 98 and later, and later versions of NT will support multiple display cards. If all works as advertised, you simply need to pop in a second graphics card into a PCI slot, power up the machine, and let plug-and-play and the multi-mon wizard pull it all together for you. Yeah, right! Actually, it probably will do a pretty good job, as long as both your graphics cards are supported by the multiple monitor wizard. Check on the Microsoft support site specific to your OS to be sure they are. (Another very good reference site is Realtime Soft, a Swiss software firm with an excellent multi-mon information section.) Basically what you end up with is large desktop spanning both monitors. Undock the instrument panel and drag it to the secondary monitor, leaving the whole of the primary monitor to display the outside. While this works, you will see a definite hit in your frame rate.
Fortunately there are some extremely talented and generous individuals who have addressed the issue of multiple monitors, and have made their efforts available to others. WidevieW is a freeware utility by Luciano Napolitano that allows several PCs to be networked together and run Microsoft Flight Sim in a coordinated fashion. One computer acts a master and provides the user interface. WidevieW passes controlling information across the LAN to the other computers and synchronizes their execution with the master. The secondary computers can be configured to display different outside views or additional flight instruments. Luciano also hosts a WidevieW support thread on the Escape Airlines Pilot's Lounge forum.
Rory Gillies has written an overview article about WidevieW and posted it on his "Shetland Flyer" web site. He has some impressive pictures of what he has been able to accomplish with WidevieW.Peter Dowson is another talented and generous individual making his efforts available to the recreational flight sim community. WideFS links MSFS98/2K/2k2 and FSUIPC-interfaced utilities over a network without requiring FS on the second computer. In addition to continuing to support WideFS and FSUIPC, Peter has also written an SDK which includes sample code. Downloads of these programs along with documentation are available on Enrico (Mr. Project Magenta) Schiratti's site.