(Also asked over on ServerFault, where I was advised to post it here too)
We have a requirement to send desktop alerts to various users (compliance, production)
The message-delivery semantics of XMPP are liable to be a good fit for your application, since you're not talking about financial transactions that require fiduciary-level delivery guarantees. It will certainly be better than NET SEND by a lot.
Write a simple client that listens for messages and does the pop-ups in whatever format you want, and have the program run in the background, perhaps with a tray icon. Writing something like that with Jabber-Net would be the work of a few hours, for example.