Unable to use sound - "Dummy output"

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http://forums.fedoraforum.org – Hello everybody, how are you? Yesterday I have installed fedora 17 on my computer. everything worked great. I bought today a PCI soundcard and installed Realtek sound drivers. Unfortunately - I installed it with a root privileges. Since then - I can't use sound. I'm not able to use any of soundcard. I get this message on the 'sound preferences': I have googled it a lot but I could not solve this problem. I really need help. How do I restore the default fedora's sound drivers? they worked great with the onboard soundcard. Thanks you so much! (HowTos)