Help, my laptop suddenly quit connecting to the internet.

Here's two no driver required devices for Windows 10.

$7.98 @ Amazon https://www.amazon.com/TP-LINK-TL-WN725N-Wireless-Adapter-150Mbps/dp/B008IFXQFU

$18.89 @ Amazon https://www.amazon.com/gp/product/B006JWMOOI

PS. Both are units I carry in my PC Rescue Kit and were used today to test the no driver hunt statement I made here on Windows 10 Home and Pro versions.

The second unit is for those that want more range.

Let's see now. You upgraded to Windows 10 and the Qualcomm Atheros WiFi Adapter worked OK for about a year. To work under Windows 10, the adapter MUST have had a driver that came as part of the upgrade package. To say that there is no driver for the adapter is poppycock.

When you upgrade to Win 10, you have 30 days to roll back to Windows 7. Past the 30 day period, you cannot do it any more.

You do not need a DVD drive to re-install Windows 10. But the real trick for you is to get the Windows install media onto a flash stick from which it can be installed. If you can get an Ethernet cable and direct non-wifi access to the internet (maybe your local public library?), you can download Windows 10 onto a flash stick yourself carefully following Microsoft's instructions. Or you can buy a Win 10 flash stick from someone who sells them, say for $25 or less. Also, write down the 25-character (groups of 5 characters separated by hypens) Windows 7 product key code from the sticker somewhere on the bottom of your laptop. Install Windows 10 but DO NOT ENTER THE PRODUCT KEY when asked for it the first time. Instead skip this step, then activate Windows 10 from the System app in the Control Panel later on.

With most Dell laptops, power on the system and keep pressing the F12 key to see the boot menu that allows you to boot from a flash stick. Use the arrow key to highlight the flash stick, then press enter. Quickly afterward, make sure you press any key to run the Win 10 install from the flash stick.

Do you have a rational reason to be using windows 10? Windows 7 does the job just fine for what you said you use it for (email, web browsing). Why mess with something that was workimg just fine? Just because Microsoft says jump, doesnt mean you have to or should for that matter.

It's possible, maybe even likely, that the built-in wifi adapter burned out. I've had that happen on a couple of laptops. If that's the case, then you're back to the cheap usb wifi solution, which is both cheap and quick. If I were you, I would just do that and move on. There's really no point in agonizing over a Win 10 rollback.

Are you sure you're not in airplane mode?

The only way that I upgrade from one OS to another is to first check out ALL of the drivers for my devices. This is especially true with notebooks as they have a lot of internal devices you may not notice on a desktop such as touch pads and those little eraser looking things. That is, they are less standard. If the WiFi adapter came with your system, you might check the support/download site for the system's OEM (DELL) and then also check the support site for Qualcomm to make sure you have the LATEST Win 10 drivers. They may also have a support notice covering your problem.

If Windows 10 was connecting to the internet before, but it isn't now, then a lack of a driver is not very likely to be the problem. Check all of your settings to make sure that you don't have something changed or switched off. This would include making sure the wifi is on (most laptops have a way to shut it off and you may have accidentally done this), making sure you are not in airplane mode or something similar, and making sure that the wifi adapter is actually working. They do sometimes stop working.

If you check everything out and it is fine, then you don't really have to worry about reinstalling. If you want to keep Windows 10, then you can reinstall it without any outside media. If you want to go back to Windows 7, then that is also possible.

If you want to go back to Windows 7, then first look for a restore partition. Most manufacturers include them on the hard drive. You can restore from that partition. Look for your exact model on the manufacturer's site and download a manual. It will tell you if a restore partition exists and how to use it. If there is no restore partition, or if you have removed it, then you will need the number from the Windows 7 sticker that was originally on the computer and an OEM CD of Windows 7 (check your computer to see if it is 32 bit or 64 bit-- you will need this information). Many computer repair shops have copies of OEM Windows CDs and may be able to provide you with one or you can ask friends to try to locate one for you. Before you go this route, be sure to go to the manufacturer's site and download any drivers for your computer because Windows will not have these included. You will need to install them right after installing Windows.

If you'd rather just keep Windows 10, then it is far easier. Go to settings, then update and security. Choose recovery and then click on "get started" under "reset this PC." You said you checked this. This will actually perform what amounts to a reinstall without removing your drivers and files. You will need to reinstall programs. If you want to replace a driver, then you will need to remove it and reinstall it.

I suggest trying the easier and less extreme suggestions first, then working your way to the more extreme measures. Also, if you do remove Windows 10, I suggest that you get a software tool that will tell you what the key is BEFORE you go back to another Windows version. Find and make a note of the Windows 10 key, which is different from the previous keys. This will allow you to put Windows 10 back on the system later, if you choose to do so.

That's the first question you ask in any formal problem analysis. If your Win 10 system was working and now isn't, something changed, you need to identify what.

Check the whole WiFi chain. Put your laptop beside your router, Can the Laptop see it? If so, then something is blocking the signal. If not, can any other WiFi device (another computer or smartphone) see the router? If not, your problem may be in the router. We had an incident here, where our ISP introduced some changes to the exchange from which the ADSL signal is sent along the phone line. Regression testing? Don't be silly, what could possibly go wrong?!!!
Anyway, during the weekend's mayhem, they sent a software update to all their own brand routers and a by product was that it turned off all the wireless transmitters! Took an hour or two to find that!

Whike you are there, plug in an Ethernet cable to the router just to check you have some signal.

But assuming your router has a wireless signal transmission, the problem is, indeed, in the laptop. Try deleting the wireless network interface adaptor and rebooting to let Windows re-install it. Sometimes works to refresh to a generic driver - or at least the one that was working before.

Still not working? Check the Windows Network Adaptor settings and reset them if necessary.

Can your network adaptor see any other networks (assuming you don't live out in the boonies)? If not, then the likelihood is that your adaptor has failed. You could buy another one and either you or your techie friend fit it. This is NOT a cheap option with proprietary parts.

The cheaper option is, as others have said, to get a USB wireless adaptor. I did this to replace an old 803.11b internal adaptor that kept getting knocked off by stronger 11n signals around. There are many such adaptors to choose from. I have a Netgear G54/N150 wireless USB Micro Adaptor, which happily transmits a full five bar signal through the length of my 22 metre house, including 3 stud walls (it's 130 Mb/s at the far end). I like it because the actual radio transceiver is half an inch wide, a quarter of an inch thick and extends out of the USB port by a quarter of an inch, so you can leave it plugged in all the time, without the risk of knocking it off.
Disclaimer, I have no connection with Netgear, most of my network gear is another brand. This thing works for me, Y.M.M.V.

Good luck!