How are you trying to open the RPM files?
Normally, you install a software package from an RPM file like this:
Code:
rpm --install somefile.rpm
and uninstall them with
Code:
rpm --erase package.rpm
For more information, type
in a terminal.
There are also graphical front-ends you can use to RPM; I don't know what's bundled with Fedora. But it is an RPM-based system so you're pretty much guarenteed to have the rpm command available.