J'ai trouvé ca dans un groupe sur google, tu peux essayer, j'ai pas vérifié si ca marchait.
2. to disable (gray out) the option on the context menu you can try a
registry adjustment. This does not work on IE4 systems in my hands but it
does work on local IE5 versions.
Backup registry before any changes please.
Note: You may have to add both the ActiveDesktop key and the value
HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\ActiveDesktop
Add a value for 'NoChangingWallPaper' and set data to 1x0
(This is also accessible in the Win98/IE5 "shell" policy editor templates.)
The reg value may activate if you just close all the IE windows and reopen
one. Removal of the value may require the reg re-set plus a reboot (Explorer
restart).
*** Slightly off point but a bit related... Some versions of the MSPaint
program also offer the ability to "set as wallpaper" -- I haven't found a way
to disable that setting short of removing the program.