This is a 1704 Dell Wifi +BT Driver
Win 7: ftp.dell.com/.../Network_Driver_3WJ6F_WN_WLAN-6.20.55.5_A03.EXE
Win 8 no 64bit drivers available in support dell for DW 1704. DW 1703 is only available: ftp.dell.com/.../Network_Driver_2CRMP_WN_WLAN--10.0.0.2_A02.EXE
Suggest you to try the above link for Win 8 as well. If it doesnt click then run in Compatibility mode (Win 7).
Also you can check in your HDD. Under C:\Dell\Drivers\3WJ6F or Network or wireless, you can get the setup file and install. Provided re-installation of OS was not done.