I have 3 HDD's, I want to install Linux Mint on HDD 3 which is currently empty and I don't want Linux to be able to write any data on the other 2 which is where all my Windows files are, is there a way to tell Linux these are read only or block them entirely?
You should be able to mount the volumes under the
/etc/fstab files with instead of choosing
defaults as the 4th option, select the
ro option with others as necessary. Details on the options can be read at
man mount 8. The option for ntfs file system may be different on your version of linux so you may have to research it more but the just of it should be the same setting the mount options as read only.
Examples of setting up the fstab could be found at these answers https://askubuntu.com/questions/113733/how-do-i-correctly-mount-a-ntfs-partition-in-etc-fstab
Example of fstab:
/dev/mapper/centos-root / ext4 defaults 1 1 /dev/sdb2 /windows ntfs-3g ro,suid,dev,exec,auto,nouser,async 0 0