Dual Monitors ?

​XPS400 2.8Gig 820 D Dual Core -VIIV​
​O/S WinXP Media Center Edition 2005​
​3 G.B. DDR2 RAM PC5300 - 2-1G.B. 2-512M.B.​
​Samsung Hard Drive 250G.B. 7200RPM​
​Seagate externial 320G.B. H.D.7200RPM USB​
​ATI 128M.B.HYPER Mem PCI-E X16 X300SE.DIM​
​ATI TV Wonder Elite PCI​
​19" FP​
​Sigma-Tel Intergrated Audio 7.1 channel​
​Logitech G15 Keyboard​
​DVD-/+RW & DVD-ROM​
​Pertelian X2040 ForeSight Systems LCD information Display​
​Dell 944 AIO Printer​
​EASYWATCH LCD System Monitor /Fan Controller​

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​ I want to purchase a second LCD monitor for my XPS400 ! B/4 I take the dive and purchase a new LCD ,I have a couple of ?'s Iam hoping the good people at Dell can help me with ? First of all can I mix a widescreen with a regular square screen LCD (my current screen is a square 19" Dell E196FP) the reason Iam wishing to add another monitor is due to having a TV Tuner an ATI TV Wonder Elite PCI ,my graphics card is also an ATI and it does have dual monitor capabilities with two 15 pin connectors. I originially was opting for a 15" as to not clutter up my desk ,however the 15" are just as expensive as the 17" or 19" (not widescreen)​

​ Once I connect both monitors and bootup my PC ,Iam assuming the system will automaticially detect the monitor ,since I will be purchasing a DEll I would expect this to be the case ? Now will my same desktop appear on both screens and then I chose from that point forward what I want displayed on each monitor ? Sorry ,Iam not a noob to PC's however Iam a noob when it comes to dual displays ! Any info or links ,suggestions etc., will be greatly appreciated.​

​ Thank You in Advance ,Nick ​