Toshiba's website is notoriously useless for drivers. Look in Control Panel>System>Hardware>Device Manager under Network Adapters and right click yours then go into Properties. Click the Details tab and take a note of the four characters after VEN and the four after DEV.
Go to http://www.pcidatabase.com and put the DEV characters into the Device input box then hit Enter. In the list that shows up, check the VEN code then you should be linked to the maker's site where you can safely download the driver.