How to find out supported Anti-Aliasing values?

I'm writing a config screen for a user to change the game's graphics settings, but I just can't find out how to discover the Anti Aliasing that their machine supports.

I've been trawling the web and checking out various forum but have yet to find a solution, as my search skill may be failing me - I was was hoping you kind folk here might be able to lend a hand?

…simply put, I need to programmatically discover the supported AA values for a user.

Thanks in advance,