Hi everyone !
( This is my first post

Will it be the bigger first post ever ?

)
Sorry to dig up this topic, but I've found a better solution to make the Sims 3 hor+ instead of vert-.
This one didn't involves memory hacking n' stuff. Just a bit of configuration.
So... This solution will work with every version of the game. Including expansion packs.
Check out some screenshots :
http://nicnl.com/trololo/Screens/WSGF/TS3/TS3-Pic1_1920x1080.jpghttp://nicnl.com/trololo/Screens/WSGF/TS3/TS3-Pic1_5880x1080_WithoutFix.jpghttp://nicnl.com/trololo/Screens/WSGF/TS3/TS3-Pic1_5880x1080_WithFix.jpghttp://nicnl.com/trololo/Screens/WSGF/TS3/TS3-Pic2_5880x1080_WithoutFix.jpghttp://nicnl.com/trololo/Screens/WSGF/TS3/TS3-Pic2_5880x1080_WithFix.jpg_______________________________________________________________
First of all, I apologize for my English and for the screenshots language.
I'm French.
Admins, please don't hesitate to modify the post and fix the bigger misspellings. Thanks a lot.
I'll join screenshots to each steps, just in case the written guide is not understandable.
I] Requirements :You'll just need to download a software S3PE. ( = Sims 3 Package Editor )
You can get it here :
http://sourceforge.net/projects/sims3tools/files/s3pe/.
And also a little bit of patience.
2] Finding all .package files to edit :Go in the Sims 3 installation folder.
( The one which contains every games, including expansions packs and stuff ! )
Search for "GameplayData"
You'll find some "GameplayData.package" files.
3] Extract original camera configuration file :Open the first .package file with S3PE.
It'll work like a glitchful version of Winrar.
Go ahead and find the file "Camera_0xStuffStuffStuff".
Right click => "Export" => "To File..."
/!\ WARNING /!\ => When saving the Camera file, the default name will be something strange.
( Like "S3_0333406C_00000000_25858B5C89C00944_Camera_0x25858b5c89c00944%%+_XML.xml" )
PLEASE DON'T CHANGE IT !!!!!The file name contains a bunch of informations, and S3PE will need them for the step 5 !
4] Mod the camera configuration file :Open the file we've just saved with your favorite XML editor. ( Mine is Sublime Text 2 )
Go ahead and search for the line that contains "kMainFOVDegrees".
You'll see that the default value is 45 : modify it to something bigger.
For my 5880x1080 configuration ( 5760x1080 + 60x2 bezel correction ) I've set a FOV of 95.
It seems to be enough to play without to many problems. ( See the "warning" under the screen )
/!\ WARNING /!\ => In the "Create A Sim" menu, the game is still
VERT- !
I think there's a way to fix it 'coz this configuration file contains EVERY parameters of the camera.
If you're feeling adventurous, you can try to mess around with maximum and minimum zoom distances, camera angle, etc...
5] Apply the modifications to the .package files :Now we've just modded the camera configuration file, we must send them back in our .package files.
/!\ YOU MUST DO THIS STEP FOR EVERY PACKAGE FILE YOU'VE FOUND IN THE STEP 2 /!\Open the .package file you want to modify.
Then, just drag and drop the file we made in the step 4 into S3PE.
You'll have a weird window, with plenty of brainfucking configurations n' stuff.
Just click "OK".

After that,
DON'T FORGET TO "File => Save".S3PE don't save automatically, so you must do it manually.
6] (Optional) Delete Sims 3 Cache :I had some problems, modifying the files didn't changed anything in the game.
Deleting the cache of the game seems to fix it.
This step is optional, but I advise you to do it.
Just go into "Documents/Electronic Arts/The Sims 3"
And then delete everything that contains "Cache".

Don't forget to close S3PE, otherwise The Sims 3 will not launch, resulting in a strange error.
I hope this will help you.
EDIT :
There's might be a way to center the HUD.
Installation Folder/The Sims 3/Game/Bin/UI/UI.package
There's a lot of XML configuration file for the HUD.
I'll search if it's possible or not.
If somebody could help me, it'll be awesome.