Try the following, assuming your using an nvidia card and that you want Pro/E on teh Right hand screen.
Enable nvidia desktop manager
Add vertical grid on LH screen, approx 3/4 width (will split screen 1 into 1:1 & 1:2)
Add hotkey (Alt+Z maybe) to place a window into display 1:2
There's a few other settings in the nview menus that you could try as well
Tell pro/e to have separate floating model tree using config & screen customisation.
Most of the time the model tree will stay in the left screen in the display 1:2.
When you switch parts it will sometimes flip back onto to screen 2.
After a while it becomes 2nd nature to quickly press Alt-Z (or maybe a button on a space mouse) and the window swithces straight to display 1:2 again.
It's not perfect but it does allow some more real estate on the 3D screen.
Almost all of our engineers use dual monitors. I did go into the NVidia control panel and set a hot key for Alt + Z to move Creo to the second monitor for a couple people that requested and It works like a charm.
Downside: Each new Creo window opens on primary monitor, must use Alt + Z to move to 2nd monitor
Here is another option:
Open nView Desktop Manager, select Applications, Add, Browse, go to the following location below and select xtop.exe, Open, OK, select the Application the xtop application, Individual Settings and match the image below. Select OK and OK from the nView Desktop Manager to close the window.
Downside: Creo is centered in the 2nd monitor, but every new Creo window opens on 2nd monitor
C:\RTN\PTC\Creo 3.0\x64_creo3-m120\Creo 3.0\M120\Common Files\x86e_win64\obj