They installed. But in the windows vm (running my host PCLOS) they are there and the VM OS says they are starting rather than saying they started. I am guessing that in that state the ability to use the bidirectional clipboard tool is non-existent. The manual for 4.1.20 vbox additions says they work in any version of windows 2000. What do I need to do to get the tools to actually start?
What I am trying to figure out is how to get the clipboard sharing to work between my host PCLOS and my guest windows 2000.
It was real easy getting it to work between my host PCLOS and my guest PCLOS after I got the vbox additions installed and working.
permissions and security are non-existent in windows. There isn't any kind of vbox group like the vboxuser group in the host Linux and vboxsf in the guest Linux.
EDIT It originally was supposed to say 4.1.18 but now 4.1.20 has come out and it is doing exactly the same thing. Apparently the vbox additions are only partially started. It seems only the mouse, keyboard, video and folder sharing work but nothing else. The only thing that I can't get working that I want is the clipboard sharing.
Just created a Win2K VM, to which I added the Guest Additions. Rebooted the VM as per request. Opened Wordpad, selected the most readable of the ugly fonts offered, then typed a test line and copied it.
Opened Kwrite, pasted the copied line from Wordpad. Typed a new line in Kwrite, copied it, then pasted it into Wordpad. Ended with a third line from Wordpad to Kwrite, then took screenshot of both. In Win2K I saved the file as Test-page.txt

I didn't do anything other than what I said above.
I shut down the Win2K VM, added the same shared directory I use for the Linux VMs. Booted the Win2K VM and mapped the share to drive E:
I opened the Test-page.txt file in notepad this time, added a line and saved it as Test-page2.txt, then copied it to the E: drive.

In the host, I open the Share directory...

...click on Test-page2.txt, and it opens in Kwrite.

I can now pass files between the VM and the host. Again, nothing fancy, it just works as it should.
When you ask how to start the Guest Additions, the question has no real meaning, because you don't start them, as such, you just use them. They are not separate applications, they are features of the VM itself. If the VM is running, so are the Guest Additions.