uninstall your sound card drivers and reinstall them.
If you dont know what your doing what im about to sugest may leave you with no sound.
**READ THIS ALL THE WAY THREW FIRST**
go into device manager find your sound card click it then click remove. then click refresh, it should refind your sound card and reinstall the drivers. If you have the drivers for your sound card reinstall them.
Reinstall direct X, go to www.downloads.com
and search Direct X, download the newest version and install.
Last option, repeat step 1, remove the sound card from the device manager list, turn off machine, remove sound card, reboot machine (without the sound card in) let windows load all the way. Shut down PC replace sound card and reboot.
Final option, if all else fails change the slot for the sound card the slot could have failed, pretty slim change but its still possible.
still nothing, time to buy a new sound card. I sugest a SB live value for under $50.
If your sound card is onboard (sound not in lower horizontal slots) then you may have a IRQ conflict with a new device. scanner? camera? any paralell port device? possibly a printer. If thats the case you may need to take it in to a shop.
i still dont know how to change IRQs i have an IRQ problem with one of my machines now and cant figure it out.