You could try going onto C:\WINNT and deleting all the .bmp's except the one YOU want but of course there is nothing to prevent him restoring them all, depends on how "savvy" he is,otherwise the answer is no, unless you have admin access and and can "policy" his logon. Rgds.
That is the biggest fool thing we have ever done. The Atomic bomb will never go off, and I speak as an expert in explosives. - Admiral William Leahy
I'd say if changing the wallpaper is the worst thing he's doing, leave it alone. Unless of course, he's changing it to something inappropriate or possibly harrassing to other users.
Life is more painless for those who are brainless.
you could use the policy editor on his local machine, I believe to get into it is poledit.exe or just try to google policy editor nt 4 This was meant to be what AD is to windows 2000