Theres basic 2xMSAA and 4xMSAA
There are two 8x AA modes.
One is 8xCSAA and the other is 8xQ
8xQ is basically 8xMSAA.
8xCSAA using 4xMSAA and 4xCSAA sample points.
16xCSAA has 4xMSAA and 12xCSAA sample points.
16xQ has 8xMSAA and 8xCSAA sample points.
AFAIK, all above listed options work on the 8800GTS.