You are getting an error because you cannot run 32-bit Windows 7 on the Satellite C640
The only drivers available for it are for 64-bit Windows 7
See driver page here: http://www.toshiba.co.uk/innovation/download_drivers_bios.jsp?service=UK
You will have to install 64-bit Windows 7 on it, or order recovery media from Toshiba via this page:https://backupmedia.toshiba.eu/
It will cost you £30 approximately if you live in the UK.