Windows Service communicates with Interactive user

[flat_ross]

I have a service running under SYSTEM in XP that needs to notify the
interactive user.

From all of my newsgroup reading it looks like it is no longer
acceptable to set the service as "Interact with Desktop". I have no
problem with that because I actually want to notify certain
interactive users. So under Terminal Services or Fast User Switching,
I only want to notify a particular interactive user.

I could run a second service or exe at startup that runs under the
interactive user and then communicate through named pipes. But I don't
want to because I don't want the user to be able to terminate the
program.

So then I thought I could do a Run As for that second exe but you need
the password of the user.

I guess I could use "net send" but I wanted to popup an MSN-style
window.

I've also looked at NtCreateToken but not sure how the heck it works
or how to get this to run under C# or VB.NET.

Anyone have any thoughts or solutions?