I recently purchased a 40" Toshiba LCD HDTV and wanted to see if I could connect my Dell Mini 9 to it so that I could use it the same way I use my Mac Mini (Web, Video, Pictures, Music, etc) in the living room. I had been running 10.5.7 with Dell EFI 1.25A without issues after doing a OSX on Runcore via Mac installation. I read throughout the forums and saw posts saying mirror couldn't be done or complicating the process for getting even an extended desktop to work. After playing around for a couple of days I was finally able to get the DM9 to drive the 40" though a mirrored display through a VGA to VGA connection. I didn't really keep track of everything I did exactly, but I think this is a pretty close description of what I did, I wanted to share it for those of you trying to do the same thing as me.
At first all I would get was a garbled mess on both displays when I connected the VGA cable. So I tried to run the Dell EFI 1.25A installer again to get the mirror friendly GMA texts installed by checking that box only after choosing "custom install", but had the same results. I would reboot and plug in the VGA cable to either garbled picture on both screens or a system freeze. I then tried installing Dell EFI 1.1 over my current Dell EFI 1.25A install and after rebooting I was able to use both displays in extended mode. I played around with the display settings in system preferences, moved the menu bar from the left to the right, didnt like it, activated mirroring and then I tried rebooting with the cable already hooked up and I was able to mirror my display. I then reinstalled Dell EFI 1.25A on top of the 1.1 and chose all the options (I first ran it with only remove custom dtml.file) including the mirror friendly GMA texts and its working fine at 1400 x 1050. It could go even bigger but then it runs a little slower.
In order to ensure decent performance, I created a second user account that is strictly for use while connected to the TV. It has less start up programs than the main usser account does, has 4 spaces instead of 6, has boxee and hulu on the dock, etc. This is also a good idea since my windows sizes wont have to be adjusted when I change from 40" to 9" and vice versa.
Here is a video of it working:
Thoughts and comments are welcome.