First, have you made sure that you uninstalled all of the first Sound Blaster drivers?
For example, Creative recommends, for Sound Blaster cards, that you not only remove drivers via Windows Add and Remove program but also through the device manager.
Might be worthwhile to remove all audio devices this way and start over.
Second, was the software CD for the Extreme or the Platinum?
If you can't tell or the above didn't work
than check out this thread, specifically post #11. Make sure you take note of post #17 as it lists the actual download location and a few hints/tips.
Hope that helps.
Pauldo