Check the master volume control located on the laptop itself, like a roller thingy. If that fails to make any difference, and the sound is intermittent, I would suggest the last resort, which is to backup files and run a recovery using the Toshiba Product Recovery that should have been supplied with the laptop. This is so that software issues can be eliminated. If it still doesnt work, then it is likely that the sound card is faulty which will be on the motherboard, which is usually the most costly part.
Other than all this, try the System Restore:
Start>>All Programs>>Accessories>>System Tools>>System Restore
This will allow you to roll back to a previous date when you reckon the sound might have been working
Kash, April 2006