Hi again
Don't worry if you haven't heard of a lot of your recovery options before. You still have several ways to either get Windows 10 working, or go back to Windows 8.1, ...or (depending on your software needs) trying a free operating system alternative like Linux Mint.
Windows 10 Anniversary Update
Yes, it has caused trouble for some machines ... but for some others, it has cleared up issues that our visitors here on the forums had been fighting for quite a while. Since it is free --- (and fairly nice when it works like it should) --- try the "hair of the dog that bit you" approach, and give it a try. Since it basically replaces a high percentage of your system files, it has a decent chance of working well. (It could almost be called Windows 10.1).
If you computer originally came with Windows 7, 8, or 8.1, it should have an excellent chance of doing well in Windows 10. Heck, one of my Windows 10 testers is an old Vista laptop (like yours: it was a hand-me-down ... it was my wife's, then my daughters, and then mine... I don't require much from a computer: so they get the newer models!)...
I would recommend that you try at least twice to get the Anniversary Update installed & working well. The first try would be to give it a go as an update. If that doesn't work well, you could try it again, this time as a "clean install of Windows". You'd save your personal files (docs, pics, videos, music, etc.) beforehand, install Windows 10 Anniversary Update edition, using the options to not save your former Windows 10 installation. Once the basic system proves to be working well, you can restore you personal files from backups (usually just copy and paste), and then reinstall any programs that you previously added to Windows 8.1.
Get Anniversary Update as an update immediately
To force the update to happen right away:
1) Click on the Windows 10 Start Menu icon
2) Select Settings
3) Select Updates and security
4) In the Windows Update tab (the top tab in the list), install any updates if there are any waiting to install. I'm guessing the Anniversary Update hasn't been offered to your system yet. When done with any updates waiting to install, and Windows Update reports that "your system is up to date" ... but the Anniversary Update hasn't arrived yet - to to step 5. By the way, the Anniversary Update shows as "Feature Update to Windows 10, build 1607".
5) If the Anniversary Update has not been installed yet, but your system says "up to date" ... you can click on the blue highlighted "Learn More" item beneath "Looking for info on the latest updates?"
6) Clicking on "Learn More" will take you to a Microsoft webpage where you can download a little installer file that can start the Anniversary Update for you. You download it to your Download folder, navigate to it, double-click on it, and the installer will begin to download & then install the Anniversary Update.
If you'd like to see those steps, complete with screen shots of each one, visit the following Windows 10 blog page:
https://blogs.windows.com/windowsexperience/2016/08/02/how-to-get-the-windows-10-anniversary-update/
And ... as I mentioned before: you can always download and install Windows 10 on your laptop at any time: because you already have "digital entitlement" to Windows 10 on that laptop.
Might as well try the update. For you, it's free, and has the highest "upside".
Going back to Windows 8.1 - using a product key.
Even if your brother didn't keep the paperwork for your laptop, the product key might still be on a sticker on the bottom of the laptop. If so, no worries, you can visit that link in my previous post, and download Windows 8.1. It would be an "iso" file - you can then, from a working Windows 10 computer (any Windows 10 computer with a DVD drive will do), put a blank DVD in the DVD drive, then right-click the "iso" file and select "burn image".... The Windows 8.1 "iso" will be burned onto the DVD. You can use that to "clean install" Windows 8.1. Remember to save your personal files beforehand!
Going back to Windows 8.1 - using a system image
If your brother made a "system image" backup before he gave the computer to you, you can use that to return to Windows 8.1. It will erase everything currently on the hard drive, so you'd have to backup your personal files beforehand.
Manufacturer's built-in Recovery
Some manufacturer-supplied "system image backups" (which used to be small enough to fit on DVDs, and were called "Recovery Disks") survive the upgrade to Windows 10, and can still be used to reinstall Windows 8.1. The problem is that even when this is the case ... it usually erases everything currently on the hard drive in the process. [The computer looks just like it did when it first came home from the store]. Look for the make/model of your laptop (usually printed on the bottom) and visit the support website for your make/model, and have a look at the user guide for it. It should have all the details you need to know to try a "Factory Restore" (yet another name for the very first "system image backup" for your computer!).........
Linux MInt 18
If your computing needs are simple, and you don't necessarily need Windows to run what you need to run, you could give a free open-source operating system a try. I use, and have helped many of my computer customers to use, a free version of Linux. Currently, I usually install Linux Mint 18 for those who want it, as it is easy for folks familiar with Windows to use (many of whom are switching from Windows XP, Vista, or Windows 8). Older versions of Microsoft Office can sometimes still work in Linux - using a feature called "Wine" to install Windows programs. This part is not-so-simple, but there are guides available that can help with that. Microsoft's Office Online is likely a much easier solution, if your Office needs aren't complicated: the Office Online programs can do basic documents, spreadsheets, and presentations .. just not with as many fancy options as the full versions .... and they have ads off to the side while you are working with the Office Online programs. Office Online is free, and it works fine in Linux, which is free: a nice combo.
So, let your pocketbook forgo any "panic attacks" ... you have quite a few free-of-charge chances to get a good, modern, up-to-date operating system on your laptop.
Let us know if you have questions.
[.... and, just in case: if no one has had you run diagnostics on your laptop, it would be a good idea to run some -- especially if you have some available when you first turn your computer on (look for a message such as "Press F12 for Boot Menu" or such). Many systems have full diagnostics available simply by choosing "Diagnostics" from a Boot Menu ... the key/keys to press will be mentioned in the User Guide for your make/model ... Running the diagnostics will make sure that you don't lose time trying to update your software programs on faulty hardware.... You'll want to make sure the hardware is OK first!]
Good luck!