No, do *not* remove alsa-lib or alsa-utils (they are core CentOS packages).
Have you rebooted since installing kmod-alsa as the kernel will need to load the new drivers? If not, please reboot and retest.
If it's still not working after updating ALSA using kmod-alsa from elrepo (after a reboot), then you might want to consider removing that package as it hasn't fixed the problem in your case:
yum erase kmod-alsa
Hope that helps.
Thanks for that advice - I've rebooted and tested again but, although the playback sound is absolutely fine the mic still doesn't work - when I try the 'skype testing service' I just get some faint buzzing sounds instead of (my) intelligible speech. OK, I'll remove kmod-alsa if it obviously hasn't cured the problem, but where does that leave me? I've only had this problem since I upgraded to CentOS 5.3 - skype worked absolutely fine with CentOS 5.0, so I'm wondering if anybody else has experienced this with CentOS 5.3? I don't particularly want to go back to CentOS 5.0, but I'm pretty frustrated that I can't use skype at the moment because it's such a useful communication facility. If I'm going to stick with CentOS (5.3), isn't there something else I can upgrade to solve this problem?
Andy