Hiya, most gfx card manufacturers have as far as I know in their infinite wisdom introduced a feature that disables the DVI port of the graphics card when you remove the DVI cable It also does not enable it when you reconnect the cable, to give a cenario; To my 8800GTS 512 I have both a TV connected via composite out and a LCD monitor connected through DVI port 1 If I remove the DVI cable, while not even having the TV out activated the TV is made the default monitor, the resolution changed to affect this and usually it messes up and manages to change the display mode from PAL/B into something my TV has problems rendering so I get a black and white picture Reconnect DVI cable from LCD monitor and I get no signal at all Things get even funnier in when installing some drivers, example; I do a fresh Vista x64 install, it's working ok and supporting my LCD's resolution but of course it is dead slow since the standard drivers are crap We install the latest drivers on nVidias site, it asks us to reboot, We get the "Microsoft Corporation" start logo, and then bam "no signal" The very intelligent people at nVidia have now decided that my TV should be the primary monitor and that the DVI output should not even be enabled! Ignoring this (because it could be a driver bug that nVidia will solve in like 20 years, not at all noticing the dozens of threads that can be found about this with some google searches) Instead lets think of it this way, we have a DVI KVM switch, and just two PC's conencted to it We switch the KVM switch from PC1 to PC2, PC1 notices that there is no longer a display connected and disables it's DVI port. ya, for real! There is a company selling KVM switches that have this problem, they designed a small device that continously sends a EDID signal to the graphics card, so even if a monitor is not connected the graphics card will still think it is, you can see it here; http://www.microwarehouse.co.uk/catalogue/item/GEFEN087 Now, in Windows XP and 2000 this issue is quite easy to solve I found out, atleast for nVidia users Under services in Windows disable the "Nvidia Display Driver Service" The PC will no longer notice that the DVI cable is removed and hotswap, KVM switches etc work just as they should... This service is linked to a file called "nvsvc64.exe" or "nvsvc32.exe" depending on if your OS is 32bit or 64bit This file has the description "NVIDIA Driver Helper Service, version 174.31" Last numbers of course corresponding to your installed driver version. Quite some help this little file provides... But infact I think it does more, on laptops I think it's responsible for dimming the display when you run on battery etc, but that is of no use for me and my desktop machine... Anyway, with this in mind I set out to simply do this fix in Windows Vista x64 too... Problem; there is no such service, or for that matter file in Vista. After some digging around I find out that in Vista this file is instead "nvsvc64.dll" or "nvsvc32.dll" it has the exact same description as the .exe in XP... It is called under the registry here; Code: [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run] "NvSvc"="RUNDLL32.EXE D:\\Windows\\system32\\nvsvc64.dll,nvsvcStart" Now I thought that removing this key would disable this "feature" I was wrong... So I thought maybe it is called from somewhere else, so I removed the file. It didn't help Windows Vista still notices when I remove the DVI cable and disables it's DVI output! Now if it wasn't for the fact that my TV that becomes the default monitor is located in another room, with no keyboard or mouse, this might not have been so problematic to troubleshoot further, but it is So I now ask for your help, have anyone got a clue on how to disable this crap in Vista? Or is it just another thing to add to my list of stuff I hate about Vista?