----------------------- If the above does not correct the issue:
First off have you ascertained that your computer has sound in general?
Do you have your sound MUTED on your computer or volume turned down so low that you cannot hear sounds? Using a desktop computer, if so be your speakers are plugged in and turned on. Were you gaming and have a headset still plugged in.... if so you will not hear sounds unless you have your headset on. 8-)
Go to Windows Control Panel. There, go to Sound and then to Sounds. Test sounds there. You can scroll down the list of sounds there until you come to the sub listing entitled Quicken. Test sounds there and other sounds. Are you able to select a sound, test and hear that sound?
If your computer just suddenly became unable to play sounds you can often quickly correct the issue by doing a system restore.
This will often repair corrupted audio card drivers if such drivers have been corrupted, etc.. Guess there is always a possibility your sound card has died.