Just a quick recommendation if any of you are having trouble running this in Win7. I was having all sorts of issues and tried a bunch of different things like running it in compatibility mode, as admin, disabling Aero, etc.
The thing that fixed it for me was to make a small change in the DungeonSiege.ini file in the U6 Project folder.
Apparently, DS has problems with video drivers that end with TnL in the name (no idea what that means). For regular DS, you can run the DSVideoConfig from the Dungeon Siege folder in your Start Menu, change it to a non TnL driver, and DS seems to run fine (granted I have not played far into anything, just testing it to make sure it works). However, it doesn't change the ini file for Legends of Aranna for some reason or, of course, U6 Project.
Easiest way for me to fix the issue was to do the following:
1) Open up DSVideoConfig
2) Change the driver to a non-TnL driver.
3) Click OK
4) From the Dungeon Siege folder in My Documents, open up the DungeonSiege.ini file in notepad. Copy the line that starts "driver_description"
5) open up the Dungeon Siege LOA folder in My Documents and open up the DungeonSiege.ini and paste the "driver_description" line at the top of the file, save and close.
6) repeat for the DunegonSiege.ini file in the U6 Project folder
Had no problems at all after that. On another note, you can also put the following in the ini file to use resolutions not available in the DSVideoConfig section:
width = 1280
height = 1024
bpp = 32
I don't have a widescreen monitor, so I haven't tried that, but it seems to run at 1280x1024 just fine. Not sure if that might have any adverse effects in gameplay for U6 Project, but it seems to run fine. Just gives an annoying 'unsupported resolution' error when you first load up the game.