Microsoft account security breach and home PC

Hi.

Recently my gmail account was hacked (no 2FA enabled, big mistake). This gmail account was also used to create my Microsoft Account. I still have access to my Microsoft account,but I cannot change the password or completely delete it because it sends a confirmation e-mail to my lost gmail, and I got a one month lockdown (of accessing critical stuff) on my Microsoft account trying to change password withan alternative e-mail. Now at this point I have pretty much accepted the gmail being gone, and the Microsoft account as well.

My concern is what to do from this point on to cut the ties between my computer and the said Microsoft account. I'm worried that since I've been using my computer with this Microsoft account, could the hacker access anything important, such as stored passwords (for various websites and applications like Steam etc.) or saved files (things on desktop or other drives) if they manage to login to my Microsoft account from another machine. I have of course enabled 2FA on anything important after the incident, but I'm worried that continuing to use the same install of Windows might somehow keep updating the initial Microsoft account about what I'm doing on the computer, such as updating my passwords and saving them. I know I rather sound paranoid but that's exactly how I am right now.

What should I do? Do I need to format the PC and make a clean install with a completely different account? Or is there a reliable way of completely severing the connection between the Microsoft account and the current install of Windows?

Thanks.

Yes, the gmail password is changed. It was not my main mail account, it was just created for Youtube thus there was no phone number defined to it, there are no means to claim it back. As I said, that unfortunately seems to be out of the question.

Yet probably because I had no other gmail account, I had entered that one during the Windows installation. And the password for Microsoft account is rather similiar, even if not the person could request a password change for it using the gmail.

Therefore what I'm asking is how I can cut the ties between the Microsoft account and the PC I own.

A different way of formulating the question might be, that what kind of data is stored and updated in a Microsoft account? Are passwords saved into a computer (browser passwords, application password etc) automatically filled in if a Microsoft account is logged in from a different PC, or are they stored locally?

I don't think I used OneDrive. Never noticed it doing anything and didn't do any backup manually. Although the sync option was turned on in the "manage user accounts" setting accessed from the start menu. There was also a red warning stating passwords wouldn't be synced because the e-mail was not verfied. But to assume the worst case scenario, is it possible to store web or application (like Steam) passwords on a MS account? (you know, the remember me tick)

I also removed the PC from the devices on my Microsoft account, there are no devices listed there right now. I'm not sure if this does flush the OneDrive backups though, hopefully it does.

I have already switched to a local account, but the C\Users name and content remains the same. I'm not sure if I did everything right and (current) PC content is cut off from the MS account.

Nope, I was using Chrome. No passes on Edge.

There are other programs like Steam or various online games that save login info on the computer though, what about those? Don't think those are cookies since deleting saved passwords via clearing browse history does not log you out of any of such applications.