Install one that has a version number greater than three.

My guess (assuming that you're on Intel-compatible {i386} hardware) would be that you need this RPM:
ftp://ftp.rpm.org/pub/rpm/dist/rpm-4....4-7x.i386.rpm
If you can't install that via rpm, you may have to do it the old fashioned way:
ftp://ftp.rpm.org/pub/rpm/dist/rpm-4....4.i386.tar.gz

Post back to let us know how you are doing with that.

Also, try not to get too dependant on RPM - it's not very flexible to the end user (What if I want to install samba in /opt, not /usr/lib , for example?), and so far as I know, only Linux systems use it. If you want a new app that isn't released by a Linux vendor / software writer (which includes lots, if not most, of the great software out there), you'll have to use something other than RPM.