Sound On Toshiba

I have a Toshiba that runs on Windows XP, which I think is about a year-and-a-half old. About a month ago, I suddenly lost the sound. At first it just become really hard to hear, then barely audible, and now there is absolutely no sound.I hooked up some external speakers (which used to work in this computer), and I can't get any sound from them either. Given that, I figure the cause is not the internal speaker hardware.I've looked at all the sound settings I can find and none are muted and are all set at high levels. Not only can I not hear sound on websites and such, but also the sound effects for the computer (such as the chime I used to hear when an e-mail arrived).