There's an important step you probably did not take, and apparently the driver install software did not take care of this for you.
No matter how many sound output devices your system has installed, Windows can only use ONE of them at a time. And there is a place that you can set which it uses. So, re-install that new card, and install its drivers from the CD. Then, of course, you need to ensure that the plugs for your speakers or whatever are moved from the sockets on the back panel of your mobo to the sockets on the new sound card, because that's where the new sound signals will come from. At this point your sound may STILL not be working.
So the important last step. Go into System ... Sounds and find the tab where you can specify the Default Sound Playback Device. It will have a small drop-down window, likely showing you that it is using the mobo's Realtek system. Click the drop-down arrow to see all the output devices you have, including your new one. Choose that one. Now, on the same screen, you should also find a similar item to select the Default Sound Recording Device. Change that also to your new sound card so that you plug your microphone into the sound card's mike jack. You may also need to change the Default MIDI Playvack Device IF your new sound card also does that job, and IF you have a MIDI device to connect. Otherwise forget about this last thing.
When done changing those sttings, back out and try the configuration and testing tools that came with your card. You should get sound from it now.