[Blackkatt]

Updated 2013-04-17!!!
On latest builds of XBMC you can select witch display to use (if its activated) so you still need a software like UltraMon or other to activate secondary display when XBMC runs. With this guide I tell you how to do it with UltraMon.

However, I just found a way to do all this on Windows 7 without any 3rd party software. I tell you how.

Start by opening notepad, add this (Windows 7)

@echo off
C:\Windows\System32\DisplaySwitch.exe /extend
start /WAIT xbmc.exe
C:\Windows\System32\DisplaySwitch.exe /external

save it in C:\Program Files (x86)\XBMC as XBMC.bat

Now run it, and this .bat will first switch/activate extended view (activates secondary display) and XBMC will launch on it provided that you set up XBMC to run on secondary display. When you exit XBMC your displays will be restored.

Windows 8

OKAY, so for whatever reason you still need this, this should do it, NOTE that you first have to start XBMC one time on the desired display and set that display in XBMC
then hit alt+F4 (quit) next time you run XBMC with this bat, it should start up on that monitor

OPTION 1

@echo off
C:\Windows\System32\DisplaySwitch.exe /extend
PING -n 11 127.0.0.1>nul
start /WAIT xbmc.exe
C:\Windows\System32\DisplaySwitch.exe /external

OPTION 2

@echo off
C:\Windows\System32\DisplaySwitch.exe /extend
PING -n 11 127.0.0.1>nul
start /WAIT xbmc.exe
C:\Windows\System32\DisplaySwitch.exe /internal

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First off, I would never had figure this out if it wasn't for althekiller, thnx

Originally Posted by althekiller View Post
Try setting the environment variable SDL_FULLSCREEN_HEAD=1. I have no damn clue where to do this in that thing microsoft calls an OS that you're running so that's going to take some additional googling on your part.

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PLEASE NOTE! Your settings could be lost. And you will have to redo them, one's.
VISTA, UAC USER? If you run Vista and use UAC, Run XBMC as admin the first time when you configure it!
INSTALLATION OF ULTRAMON UNDER WINDOWS 7 Read step (5.)
PROBLEM WITH LAG? Read step (6.)

HOW-TO start XBMC in full screen on secondary monitor with custom resolution

Setup. . .

• 1. Downloading UltraMon, http://www.realtimesoft.com/ultramon/
  
• 2. Make a shortcut to XBMC.exe if you don't already have one. Place it on your desktop (or wherever). Right-click on the shortcut select properties.
  Set the environment variable SDL_FULLSCREEN_HEAD=2 (2 for secondary display) apply and exit...
  

ex: "C:\Program Files (x86)\XBMC\XBMC.exe" SDL_FULLSCREEN_HEAD=2

• 3. One's again Right-click on the XBMC shortcut. As you can see UltraMon have added two new tabs, "UltraMon - Display" & "UltraMon - Window"
  
• a) Click on "UltraMon - Display" check "use custom settings" choose resolution for "secondary display" ex: 1920*1080 and check as enable.
  
• b) Click on "UltraMon - Window" check "use custom settings" show: [normal] on monitor 2 (or whatever display/monitor you like but HEAD="x" must be the same) apply and exit...
  

• 4. Launch XBMC, change resolution to AUTO, test resolution. XBMC will automatically choose the highest resolution possible for that display.
  
• a) Now select 1080i (this will make the settings stick) and your done!
  

Troubleshooting. . .

• (5.) Download UltraMon 3.0.5 Beta or newer. Or do the following.
  
• a) Install UltraMon, ignore the errors.
  
• b) Run regedit, change these entry's
  

HKEY_CURRENT_USER\Software\Realtime Soft\UltraMon\3.0.4\Window Buttons - Maximize to Desktop Button - change value to 0
HKEY_CURRENT_USER\Software\Realtime Soft\UltraMon\3.0.4\Window Buttons - Move Window Button - change value to 0

This should fix it.

• (6.) This is a Windows problem with some blame on nVIDIA I guess.. You can solve this easy by following these simple steps.
  
• a) Right-Click on XBMC.exe, goto "Compatibility"
  
• b) Now check, "disable visual themes" "disable desktop composition" "disable display scaling on high DPI settings"
  

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There seems to be a problem that cause XBMC not to fill the screen right? Cause of this I don't know but here is plausible solution by gstreet

Try this:
1. Get UltraMon.
2. Copy your XBMC.exe
3. Right-click where you want your shortcut and press "Paste shortcut"
4. Right-click your new shortcut, select "Properties.
5. In Target, add -fs. Should look like this: "C:\Program Files\XBMC\XBMC.exe" -fs.
6. Press apply and select "UltraMon - Window" tab. Select "Use custom settings" and choose Monitor2, then also select "Centered".
7. Hit "OK", open the shortcut, should now be displayed on your screen of choose.
8. Go to your skins settings and choose wanted resolution.