OK. I changed the
HKEY_LOCAL_MACHINE\SOFTWARE\Xidicone\Agent SVN\ActivateExec
key to "", and got the configuration dialog back.

Now things seems to be working. Two new questions:
1. Is there a way to replace the diff and history dialog boxes to use another tool (such as TortoiseSVN)?
2. Why do I ...

How o I change AgentSVN's configuration (after setting it up the first time)?
Selecting:
Project->Source Control->Agent SVN,
just brings up the tortoiseSVN repo-browser

OK. After deleting *.opt and *.ncb, I managed to get a little further.
My current problem is that I get a message

Could not connect to source code control project "aaaa".

Could it be due a problem with my evaluation license?
How do I fix that?

I just got back to setting-up the integration.
I have a project tree that looks something like:
Root
A
B
C (the project file is here)
D

I changed the .dsp and .dsw files as ordered (although I was not sure about the actual project directory. Should it be "Root" or "Root\C"?)

I still get error ...