Firstly, if it is the sound card I doubt very much that you will be able to buy a new one and fit it. The sound card is probably fitted straight to the motherboard so cannot be removed or replaced.
It could be that the driver for the sound card (and maybe other devices) has not been installed. Laptops often have special drivers that are not included with Windows and usualy need installing after Windows is installed.
If you got a CD with the drivers on it then try to reinstall all the drivers.
If you have not got the CD with the drivers on it then download the drivers from the Toshiba web site.
Dont just install the driver for the sound card. Laptops often need drivers for other components on the motherboard before the sound card will work so install all the drivers.