Never ever had so many problems!
I tried to (re)install 7 and the whole lot crashed almost at the end. As the computer didn't react anymore I changed the original HD, which was working perfect before, onto another one and started the whole procedure again. Now all went well only............ 7 isn't recognizing my router anymore: "error 651 (the modem (or other connecting device) has reported an error"
I'm now stuck again. I'm making this post via the second desktop (7) which has been connected to the same router.