Windows questions are NOT on topic here.
Now that's out of the way, lets discuss damage done by a Linux distribution's installer.
There are two topics I regularly see:
- (how to roll back) how to reverse damage done by a linux installer. (the answer could be about what the installer does and therefore how to undo it) In particular discussion Legacy boot sector and UEFI entries along with a mention of BIOS being able to select between UEFI entries.
- (how to fix forward) how to persuade grub or other boot loaders to find windows (where nix boot loaders could be considered on topic).
One of the biggest arguments for having stock answers to this on unix.stackexchange.com is "if not here then where". Most Windows questions we would still bounce to Superuser.com. But given the damage has usually been done by a Linux installer, it feels inappropriate to expect Window's experts to know what a linux installer has done. That knowledge is more likely to be found here.
Marking a question as duplicate is much more helpful than simply downvoting and closing. It's also a lot less unfriendly which is a common discussion point of stackexchange at the moment.
So a few stock answers for questions like this might be useful: Can't boot to windows after installing Ubuntu in UEFI
These questions typically have too little information to answer categorically. That's frequently because people who need to ask already know too little to include the right information. These are typically newby questions.
However when you consider the questions I believe it should simple enough to come up with a "blind" checklist of things to try.
Find out legacy or EFI then try:
If legacy then try:
If EFI then try
If all this fails then this is a windows question so try searching on Superuser.com
It takes some grace to apply this well. I note some users are averse to re-framing another OP's question in order to bring it on topic, even where the meaning is not changed. The question I reference above is framed as a Windows question, but could arguably be described as matching either "how to reverse out grub" or "how to fix grub". My own view is that we should look at the inference of the question rather than playing buzzword bingo to determine whether it is on or off topic.
dd if=/dev/zero of=/dev/sdais clearly a Unix question!