it's highly possible you might not WANT windows 10, but windows 10 damaging your computer is NOT HUGELY likely.
You'll need to check your hardware is compatible but the main thing you need to do is work out if windows 10 is the OS for you.
Let us first discuss what "damage" means,
if we consider damage as in hardware damage, anything that can't be fixed by reinstalling a good OS or using system images and repair discs to return the system to it's current or factory state then NO, windows 10 won't do damage. If it runs awfully the computer hardware could still n principle be taken back to working order as it currently is in, or at it's factory fresh state. Whatever you want to do make sure to make a system image now:http://www.bleepingcomputer.com/tutorials/create-system-image-in-windows-7-8/
WHATEVER YOU DO MAKE A SYSTEM IMAGE, IT'S GOOD FOR FIXING OTHER TYPES OF PROBLEM TOO
if we consider damage to mean ruining the OS and having an OS that can't work well with your hardware, perhaps driver issues and incompatibilities, yes this can happen, especially for older hardware.
if we consider damage to mean changing the system so it works in ways you don't like but which are designed into the OS, this is entirely possible. Gp and have a look at a computer running windows 10 already, see if you like it, if not then don't upgrade your own and don't let your own be upgraded. Look at news about windows 10, see what people are ranting that they hate*, if you're ok with the things it does then you might consider upgrade.
if we consider damage to mean removal of programs so they'll need reinstalling later, this is almost certain I think.
You should be taking immediate actions to make sure that the decision is made by you not by automatic download behind your back, until you've decided if you want windows 10 remove all windows updates that are not security fixes and set windows updates so they are "check automatically but ask me whether I want to download". Especially remove KB3035583 and updates to the windows update client. Check your C: drive for a folder (likely hidden) called $WINDOWS.~BT, if you don't want windows 10 you'll need to remove this folder.
*things it is widely known to do and does in all cases, not rare bugs and bad luck but actual design features of the OS which people don't like
Edited by rp88, 21 April 2016 - 02:09 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB