What is MySQL doing?? 100% disk utilization from boot

I have a large database on a Win10 machine, mysqld.exe does a lot of disk I/O, 100%, for hours and hours 100MB/s consistently - mostly writes - persists after numerous reboots. How can I find out what the hell it is actually doing, and stop it? I know the database is not being used at the moment, I want to figure out where this I/O comes from and stop it. The only solutions I found on the internet were general configuration advice, I don't need that, I need to shut this thing down now!

show processlist shows nothing.

UPDATE: The problem was a huge background rollback operation on a table. The solution is:

1) kill mysqld.exe
2) add innodb_force_recovery=3 to my.ini
3) start mysqld.exe
4) export the table (96GB table resulted in about 40GB .sql file)
5) drop the table
6) kill mysqld.exe
7) set innodb_force_recovery=0 to my.ini
8) reboot and import the table back

No idea about data integrity yet, but seems fine.

Thanks to Milney.

If you view the Disk tab of resource monitor from Task Manager you can see which files are being written, this will hint you as to which Database it is;

You can then use something like SELECT * FROM information_schema.innodb_trx\G to view open Transactions and see which statements are causing this