OK, I don't see where you specify which Toshiba Satellite L555 model you have. The Toshiba site needs L555-S????. For instance I notice for L555-S7001 there is a BIOS update from 5/20/2010, it won't fix this issue but may affect many things so if you have a BIOS update you should apply that. There are also LAN drivers and WiFi drivers. And there is a Multimedia Application - Media Controller <<-- this is likely your current issue, please try installing that. There are like 4 pages of drivers etc. Always try the latest version first - example LAN drivers from 2009 and from 2010 - get the 2010.
http://www.csd.toshiba.com/cgi-bin/t...t/jsp/home.jsp
Click Product Support. Enter your Satellite model. Click the
Downloads tab. Enter W7 64bit for your OS.
There are a lot of drivers and some reference materials available there; you should spend a lot of time there making sure your drivers are up to date.