Hi Doug,
On a Dell Optiplex 745 with onboard Intel HD, rat doesn't work with ALSA (I can't remember the error message, but something about unknown channel), but does work with ALSA's OSS compatibility layer when OSS is selected within rat.
I'd be interested to see any error messages you can get - Is that running AG RAT or the newer one (or new UCL RAT)?
Thanks,
Piers.
Doug