I looked at alternate shells for WIndows that provide support for virtual desktops. I've found http://www.sharpe-shell.org and http://www.emergedesktop.org/ Are they stable enough to be used in work environment?
I have used 2 alternative shell for Windows in the past (but not those you mention, and it was years ago), and those were certainly stable enough.
But really, you should just try them and decide for yourself.
What operating system are you running?
Here's a list of a few more: http://en.wikipedia.org/wiki/Desktop_shell_replacement
Never used one extensively myself. I'd certainly do extensive testing before I'd rely on a 3rd-party shell for a work environment.
If all you really need is virtual desktop support, there's a whole slew of 3rd-party tools.
Microsoft PowerToy for XP: http://www.microsoft.com/windowsxp/downloads/powertoys/Xppowertoys.mspx
And a few others kicking around:
For even more, see a google search: http://www.google.com/search?q=windows+virtual+desktop+manager