I have seen a lot (really tons of them) questions regarding "I can't see [Windows] partitions while installing Ubuntu".
A common property between all of them is that almost none of them has close votes for bug. Why??? It should be closed as such because .. it is a bug!
Also some of them provide more information that others, but that is not relevant (IMO).
So the thing is, lets close them, and if someone has/found a workaround lets link them as dupe!
Here are some of them, but is easy to find more: