OK, I remember SoS when I used Mandriva. It was a pig to set up as a urpmi repository.
However I have since found
http://rpm.pbone.net/ .
Next to the search bar click advanced search, then uncheck all, then check Mandriva 2006.
Now in the search bar, enter qt3-common.
I've just done this and the 3.3.6-5.1.2006.Sos version was there.
This rpm search site is the best I have used. But it means that dependencies have to be solved one rpm at a time. One way to shorten this is to put all the needed rpms in one directory, desktop will do or wherever you download to and run command in terminal as root:
cd /home/[username]/Desktop
urpmi **.rpm
This will install all rpms in the directory you are in simultaniusly. Then if a dependency is needed, simply add to directory and then run command again.