Here we go my first encounter with Sharepoint and this is the problem I get when installing WSS 3.0, admittedly this was for me the second try at trying to install both times I recieved this error haven't a clue what the original error was.
I found the problem related to the installation not removing itself completely, I had to go into IIS and remove the "SharePoint Central Administration v3" virtual director completely after un-install then I reinstalled without any problems.
Hopefully this will help you out as it did me.
I've also read an IIS reset / restart of Windows Sharepoint Services Timer service will also help though I didn't need to use this myself.