Dual OS Drive access problem

Windows 10 pre-installed is almost always installed UEFI. Did you install Ubuntu in UEFI mode?

When you say 'drives' do you mean partitions or do you mean physical hard drives? In Ubuntu if you are using the default Unity Desktop, you should see hard drive icons in the left panel where you can access other non-system drives/partitions. You can also go to the /media/user directory and access them by UUID. Have you tried that? If you don't know if you installed Ubuntu UEFI, go to the site below and get the boot repair software and download and run it in Ubuntu. Select the option to Create BootInfo Summary and post a link to the output here. Do not try to make any repairs.

https://help.ubuntu.com/community/Boot-Repair