Active Horizontal Pixels and Active Horizontal Lines should do it. Set this to the same resolution as on top.
Scaling should be left to "adapter", that's how I found worked best. But this is something you can play with.
I notice that in my screenshot I have here I don't do it anymore on 1080p, but I had to before, I completely forgot the newer nvidia driver did the job for me.
But in your case those settings should do it.
Thanks for the time you spend on my problem, but that doesn't work...
I created a resolution 1024*576 when i'm in 1080i, but when i use it i don't swith in 576p...
And when i'm in 576p, i don't see this custom resolution anymore
I have found the key to modify in the registery to swith from 1080i to 576p and back, but i still need to restart the htpc for the change to be applied. I tried to kill the explorer.exe process, but it does not work...
Does anyone know, if there's an other way to apply the changes in the registery ?
Hava you checked the specifications of your A/V receiver?
It may be that your problem came form the fact that many A/V receivers only have a switching matrix inside. They don't mix/convert between signal. That means that you only can have the kind of signal you need at the output if it is present at the input in the first place (S-Video to S-Video, Composite to Composite, Component to Component or HDMI to HDMI).
If this is your case, I think the only way to do what you want is to connect the s-video output of your video card (that's if your card has one) to your A/V receiver in parallel with your HDMI (or component) one.