I gave up. I uninstalled MOSS2007 and created a new DB. Now I have a clean wroking MOSS2007 server.

But there is an other issue: I cannot import the content db

The error message is the following:
The specified spcontentdatabase name=wss_content parent=spdatabaseserviceinstance name=SFI-SPS-SZERVER\OLDSFISPSDB has been upgraded to a newer version of sharepoint. please upgrade this sharepoint application server before attempting to access this object.

I checked: and the MOSS2007 SP2 and WSS3 SP2 are installed
Before it was a standalone server, now it is a farm.

What can I do?