error message while trying to install additional packages

[Thomas Kirk]

problem installing additional packages on ydl 4.0
This is the exact error message I received after executing the
following command:
/usr/share/system-config-packages

checking system package status
the package manager is searching your system
to determine which packages are installed

installation tree not found
the path /mnt/cdrom does not look like a valid installation source.

i am also getting the following error message when i try and run yumi and
gyum
"runtime error: bad magic number in .pyc file
When I try and remove them, i get the message that the programs are not
installed.
 and when I try and reinstall them i get the message that they are already
installed.
I would appreciate any guidance or information you could direct me toward.
Thomas Kirk