Christ almighty. The OP asked specifically about a solution for Windows. Most of the posts at this point are from the usual sad bastards who think 'Linux' is the answer to any question. For a Windows user, scrubbing the entire work environment and starting again with an unfamiliar or just plain unsuitable OS is not a solution in any universe. You lot do nothing to help your cause at all.
Ok, most Linux WMs have a virtual desktop manager built in, the Gnome one (or even the CDE one going back to HPUX or Solaris) are perfectly adequate, but for a Windows user you might as well suggest kicking themselves repeatedly in the nuts if that's the only advice you have to offer. Windows doesn't have a virtual desktop option built in, but Linux does, awesome, that's 1:0 to Linux but still totally fucking useless.
For my part, I've been looking for a similar solution. I've played with one or two but not found anything particularly useful. The OP's post was useful in itself in that he posted links to the ones he's checked out himself. A quick look suggests that Virtual Dimension looks good - I'll be checking this out myself. I have 3 monitors, two of which are generally dedicated to email and my knowledge base. PuTTY sessions generally sprinkled across the three. Being able to switch my entire screen environment for particular tasks would be useful.
Extra info for Linux fucktards: I'm a 20-year Linux admin and systems programmer who pretty much HATES Unix window managers and prefers Windows as my main desktop platform. I've used lots of Unix desktops and frankly they're mostly a disaster in my opinion.
And those of you who have posted useful info in response to the OP's question: thanks, very useful.