I'm glad I'm not the only one who's getting seriously annoyed by these ads. I have the same ads popping up on all message windows. Here's what I've tried so far:
Had 2000a installed originally on Win2k and 98SE. Got the ads sometime in the past week, and after seeing they had no intention of leaving, got ticked off and left ICQ for a while. Then I see this thread and start tinkering.
First try - removing 2000a and installing 99b, and attempting to run the database converter. After getting dbconvert to see the 2000a databases, it spent a while working on it and seemed to reindex the database just fine (found all users, found correct number of records, etc). BUT - 99b crashes with a Visual C DLL error dialog at startup with this converted database. No go, but there's potential here if somebody can figure out what it is about this converted database that 99b crashes about. So close, the database was converted, but....
Second try - reinstalled 2000a, got databases back up and running, and then deleted the three ad DLL's, blanked out partner.xml, changed the two registry keys for Transaction set to "No", and set AutoUpdate to "No". This was all done with a disabled network connection. I ended up with the grey background ad box and the ATEBROWSER message. Better than having ads, but still not there.
Third try - by this time the registry was getting pretty congested with different ICQ versions being tossed around (at one point I brought 98a back from the dead to see what it could do). So, I cleaned off a drive and installed a fresh copy of 98SE. With connection disabled, I installed 2000a, did the registry corrections, and found none of the ad DLL's in the directory to delete. Also, no partner.xml file to blank out, presumably because ICQ hasn't been "upgraded" yet. I signed up with a new test account to try to eliminate the ads being tied to my database files. No go. Ads were back. Reinstalled database files, and ads are back there, as well. What's worse, there are none of the ad DLL's to delete, and so for now apparently I'm stuck with the ads. The temporary solution is placing all message windows so they pop up at the bottom of the screen with the ad space hidden behind the task bar. This is working surprisingly well, so I'm fine with using the software for now, but we still need a permanent fix that gets rid of the ad box.
The OCX file seems to be key, because of the ATEBROWSER references and HTML code present in the file. This OCX file was present in all of the installations, at least. Also note that the SMS message was trivial to get rid of compared to the ad boxes.
One last interesting thing...after finally finding a clean way of getting rid of the ads and ad spaces in AIM, I saw files that had similar names as the ad DLL's as ICQ. The ad remover got rid of these files, so I'd have to reinstall AIM to make sure, but at least two of the DLLs were the same (the res DLL was not present). Unsurprising of course because it's all AOL, but this also means whatever exploits were used with AIM can be used on ICQ as well. Search Google for "AIM ad remover" for some of the ad removers available.