I want to install Ubuntu/Lubuntu over the top of the C: drive where Windows 10 is now installed, removing it completely while preserving my data on the other partition doesn't gets formatted.
Is there any way to do that?
Yes, there is a way to preserve a data partition while removing Windows 10 and its partition, but first, we must be very careful to do six things:
When you are absolutely, positively, done with Windows 10, then click on the windows button, click on the power icon at lower left, and while holding down the Shift key, click on Shut Down. This makes sure all changes are written to disk and the disks are released.
When 1-6 are done, then you can install Ubuntu / Lubuntu / *buntu. When it asks where to put Ubuntu, you choose Something Else and specify to put *buntu where Windows was, while not changing the other partition where your data is.