thoses are not artifacts. That is actually quite normal on older card.
Read this page and i think you will see its not a problem and its quite normal.
http://www.bit-tech.net/hardware/200...ltering/2.html
your only problem is that your card is probably not powerful enought to bump up AA.
EDIT: Also this will show
http://www.bit-tech.net/hardware/200...ltering/5.html