Program doesn't display to desktop

[BiggJohn]

Good Day,

I have a script which runs an executable which displays a prompt on the desktop.  It is run as the local system account by our automated desktop management software.  It runs fine for most users, however for some, the on-screen prompt never displays, even though the program is running in the background.  The common theme on those systems having this problem is that when the script executes, there is no one logged on, and when they do log on, the process is running, but does not appear to them.  Procmon shows the process is running and also displays a message box saying "No visible windows found for this process".  The line that executes the code looks like:

$COMMAND = "c:\windows\proc.exe"
$Options = ' /options that extend to another line' _
& 'Message in box'
ShellExecute ($COMMAND, $Options,"c:\windows\")

So I'm wondering, is it possibly because I used ShellExecute?  It needs to be said that about 90% of systems run this just fine, and in testing I have successfully run it while logged out and had it display when I logged in.  Any thoughts are appreciated.

[BiggJohn]

Any thoughts at all??

[markyrocks]

I'd say have the script look for the window,   if it's not available,  have the script reload.  Or check to see if someone is logged in or not and to only execute if someone is logged in. 

[AutoBert]

What are the differences in OS (Version and Type), proc.exe (Version and Type), Firewall, AV etc. Did the behaviour every time occur for the 10% or differs it from time to time?. Is the executable also from you? Maybe a look in the source would help finding the bug.