Help With Creative Sound Blaster Audigy 2?

So I bought the Creative Sound Blaster Audigy 2 sound card and installation stuff for my laptop. On my Dell d620 im running windows xp and there's a mute on right above the keyboard. But when I hit the mute on, it doesn't stay mute. It stays mute only if i hold the mute on but before it had worked fine when i first installed the soundcard. I don't know what I can do to fix it.