Go here and enter your laptop's service tag (underneath on a sticker) and click "Submit":http://www.dell.com/support/drivers/uk/en/ukdhs1/DriversHome/ShowProductSelector?fkey=Drivers_PS
If service tag is missing, click the radio-button for "Automatically detect my Service Tag for me
" and click "Continue".
Note: If you choose the latter option (auto detect) you must do it with your Dell laptop connected to the website, not a different PC. So if you don't yet have wireless working on it, use an ethernet cable to connect it to the router.