a few things
Fedora is not a good choice as a "first" linux install. It can be good BUT and it is a big but
fedora is a R&D distro .Not everything will work all the time correctly ( it is better than it was back in fedora 4 to 10 ).But updates can and will break some things,from time to time.
If you DO want to learn how to fix things , hack source code in order to build and install some programs ( not everything will build in fedoras " bleeding / cutting edge" software .
it is good IF YOU WANT TO LEARN by doing/ fixing things .
BAD if you are looking for a " just should work" distro. For that look at Ubuntu,Debain .Mint and a few others.
ROOT login to the GUI Gnome and KDE ( kde sort of works) was DISABLED back in fedora 10 for SECURITY and user safety reasons .
There is a hack - BUT IT IS NOT
" sudo" -- this IS NOT configured by DEFAULT for security reasons ( there is a security hole in it - a very big one)
"su " and " su - "
Fedora uses the " su - "
you might want to do some research on the two
most things in fedora that need root access will not work using "su"
the pam.d ? might? be a SELinux permissions ( it is a known bug - it happens from time to time )
is there a gold/yellow star on the top toolbar in gnome ?
if so launch SELinuxTroubleShooter and fallow the instructions.
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you might also want to read the fedora documentation
and the fedora 12 user guide