Problem solved, new problem

I responded too early. I have now seen the response of Peter on 29 March.

SOLUTION:
The link to the file was: file:///c:/program files/networking/pac/no-ads.pac. I started to mess around and finally changed it to: file://c:/program files/networking/pac/no-ads.pac.
Leaving one slash out did the trick...

@the creator: You might want to change the comments. I copied the mentioned link from the installtion comments. At step 3, configuring IE, it gives the wrong link. I am using IE6sp2.

NEW PROBLEM:
By the way: it blocks popups that I DO want (when I click them). I made a change the "re_banner" variable, and tested it. It now shows the popups I am looking for.
Still I didn't have the time to study why this works. Can anybody tell me what implications this might have on other URLs?