So I have been wondering for a while how usable KDE 4 is as a shell for Windows. The answer is it it not quite there yet some essential pieces and parts are still missing. This should work for all Windows 2000 and above.
1) open regedit (start menu > run, and type in regedit).
2) go to: HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon.
3) add a new string value (Edit > New > String Value) called shell. and set the value to the path of the new shell e.g C:\Program Files\KDE\bin\plasma.exe
4) log out and log back in.
This changes the shell only for the current user which is a good thing.
Quick run Down of what I have found to work and what does not. For this look I’m using 4.1.80 the beta for 4.2 it may not apply to older or newer versions.
Task Manager Plasmoid – Missing
System Tray Plasmoid – Missing
New Device Notifier – Present but not functioning correctly, fails to show any new devices
Menu ( Kickoff or Classic) – Both are present, and work great except that you have no way to access your Windows Specific Programs i.e. anything installed to your Start/Programs menu and none of the Leave Functions work( logout, lock, etc).
Quick Access Plasmoid – Missing, this could be used to access the Start Menu until that functionality
Quick Launch Plasmoid – Present and working, no way to add windows applications.
Also Plasma needs to be hidden from the Task Lists and Z-order of containers like the desktop and panels need to be enforced.
I feel like all of this is intentional.
By design, KDE-windows does not provide the full-blown KDE desktop, a preview on the plasma shell replacement will be available in 4.1.2 – Nevertheless this does not rely on kwin/X11 which means that desktop effects are not available – KDE TechBase Wiki
Are we sure that cutting out features is the way to go? I understand that there are some things like Konsole that my not be possible do because they are to deeply rooted in the way*nix works. Users should be able to pick from everything the KDE system offers and not be limited artificially.
No, I mean it, maybe.... 
This is a great website and nicely put together.Thanks for letting me view it.
I would love to be linked to your site.
actually there are some people working on this stuff. browse the kde-windows mailing list. right now their main target is to get applications running though…
That is good, they have already done a great job getting KDE working on windows, perhaps I should have stated that in the article. I used to use LiteStep as my windows shell when I a full time windows user. It is a very niche area to start with but there are great examples of how to these things in KDE.
hmm…I’d love to try this but my question is, is it reversible? I dont wanna go hacking up the registry.
This is absolutely reversible, all you have to do is remove the shell string from HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon or set it to explorer.exe . Using ctrl-shift-esc will call up Task Manager regardless of your current shell.
I tried it and was very disapointed to find, well…the lack there of. It looked just like it would I I’d just ended explorer.exe. But a lot of KDE processes were running. Not sure what went wrong.
I just finish the installation of KDE 4.3.0.
In “Advanced” tab, “System Setting” there are a “Platform” icon. It has a “Windows Desktop Shell”. Options are:
-Native desktop shell (System’s default desktop shell)
-Plasma desktop shell (KDE4 Plasma desktop shell)
-[Setup…]
OK, that section is disabled right now.
But i hope it will be enabled soon.
Same on 4.4.0 and none of the missing plasmoids appeared :(.