If you installed FC2, then you might need to configure the ALSA drivers to work with kernel 2.6.x. Fedora FC1 didn't have this problem since it used kernel 2.4.x and used OSS sound drivers. Kernel 2.6 uses ALSA now instead of OSS. It can be a pain in the a$$ to get it to work.
Search the Fedora forum and you'll find plenty of posts regarding sound and kernel 2.6