My Dell Latitude E7740 Win 7 64bit laptop stopped connecting to the internet one day, so I checked device manager and I'm missing a network controller. I have the yellow exclamation mark on it, and the ID is VEN168C and DEV0032. From there, I don't know what driver to install. I tried to search for solutions, but nothing really helped me.
Any help would be greatly appreciated.
Chance are you are infected. Despite that, the best source for drivers is ALWAYS the manufacturer's site. There's no such thing as an "E7740" so more than likely it's an E7440.
There are several drivers available for download. Also I notice a button to "download an operating system recovery image". Usually they charge about $30.00 for these. They want the service tag so I can't tell if it's free or not. If it's free you should get one, save it, convert it to ISO and make a bootable USB drive and store that drive someplace safe for emergencies, such as the infection is so bad in your computer that it permanently pooches the O/S and you have to do a New Install. It might let you do a Repair Install.
Also there might be some kind of software that will automatically update all the Drivers for you. Some people like this as manually fussing around with each and every driver is a PITA and only weirdos like myself actually enjoy it.
While you are here you should look at all the various updates available and why they are there, sometimes they are "critical". BIOS in particular is something to look at and think about. DOING the BIOS flash is a different equation, but at least look at it, know where you are in the BIOS sequence and know what's available should you decide you need to do it.
I'd do the chipset drivers. Last update Jan 2016 and it is "recommended".
Okay so anyways killing off the network is like step one of malwares plan to take over the world. If you symptoms start to increase you should stop troubleshooting symptoms and start fixing the cause of the problems, which is probably going to be malware.