Where can I install network adapter and how?

I have a HP Compaq dc7100 CMT (DX438AV) which is windows xp and I updated it to windows 8.1 now I was using my iphone for personal hotspot then I opened it right now and it won't connect anymore. I clicked troubleshoot then it says problems found. The Broadcom NetXtreme Gigabit Ethernet adapter is experiencing driver- or hardware-related problems. I checked my Device Manager then I don't see any Network Adapter.

Please Help ME REASON WHY I'm USING THIS COMPUTER BECAUSE OF SOME PAPER WORKS.

Is suggest buying a Wi-Fi dongle as small usb powered Wi-Fi receiver

Know how to install network adapter, call IQ Techline at their toll free