Run scripts after installation
Solution 1:
You can use a "preseed file" to execute commands during Ubuntu installation. A specific parameter is a "late_command" or "success_command" which will run once most of the system is installed. You can add mount entries to fstab, or even lines in rc.local, here so when the system first boots it will mount your Windows partition.
Read more about preseeds here: https://help.ubuntu.com/lts/installation-guide/amd64/apb.html
There are several ways to supply a preseed, which is the best depends on what your install environment looks like. Do you want to do this for several computers at home? Need to provision several dozen systems for a school lab? Need to deploy on hundreds of computers at a company? This will influence what the best way to provide the preseed is.