What web cam is compatible with Windows 2000 and Skype you ask? You have purchased three of them and non seem to work with Skype. You have installed DirectX, but not sure of which version.
The mystery to you is that you can make a camera work, as long as you don't connect to Skype. You know a camera works. You have Skype 4.2.
You guess you should return this web cam and buy one from Skype, at least you would know that camera is approved. How does this plan sound? You can get a web cam to work without Skype, but when you sign onto Skype, and do a video test, you have gotten two messages.
One is to upgrade your DirectX and another is to update some drivers. You have done both and still Skype won't recognize it. I think a fact your running Windows 2000 might be a root of your problem.
If you haven't already, download and install Skype 4.2, which is compatible with Windows 2000. Also, make sure to install Direct X 9.0, which is needed for video calls. That webcam supports MSN and Yahoo video chat for whatever it's worth.
You can verify your Directx version by going to "Add/Remove programs" in Control Panel. If any other version of Directx besides 9.0 is installed, I suggest removing that version and installing 9.0.
Possibly your webcam will work with Skype, if not purchasing one from them that is certified makes sense.