Hmmm...the Toshibe website doesn't list an A26-S279 model...but it lists an A25-S279, Specs A25-S279.
I don't know what to make of that, especially in light of the fact that there are various websites (other than Toshiba) offering driver downloads for A26 models.
Do you have the CDs which came with your system? Did such include a CD labeled as containing drivers?
Start/Run...type devmgmt.msc and hit Enter. Do you see any yellow marks by anything? If so, please list each item with such.
The default program for opening any type of file (.mp3, .wav., etc.) can be changed by changing the file associations from Explorer view of My Computer.
How to change file associations in Windows XP - http://support.microsoft.com/default.aspx?...p;product=winxp