Been trying to fix my friend's laptop and after a format I installed all the necessary drivers but there are some problems with the network drivers. I got the Windows 8.1 drivers from here (1) and I tried both the versions available but there's some trouble, the "Network_Driver_C7DY0_WN32_10.0.0.309_A04.EXE" one prompts "The update installer operation is unsuccessful" (error log pastebin (2)) and the other one "Network_Driver_GR38D_WN_6.30.223.245_A03.EXE" tries to install the Bluetooth drivers first and comes up with "Activate Bluetooth using Wireless Switch" and I've already switched it on via fn+F2 and the bluetooth icon even shows up in the "hidden" menu from the taskbar.
(1) http://www.dell.com/support/home/in/en/inbsdt1/product-support/product/inspiron-15-3521/drivers/advanced?os=wb64a
(2) http://pastebin.com/kG4bTqAM
(1) http://www.dell.com/support/home/in/en/inbsdt1/product-support/product/inspiron-15-3521/drivers/advanced?os=wb64a
(2) http://pastebin.com/kG4bTqAM