Cannot mount sda1: "The device '/dev/sda1' doesn't seem to have a valid NTFS."

To get the exact information about the bootable windows partition before executing ntfsfix:

sudo file -s /dev/sda1

Then use ntfsfix to fix this problem:

sudo ntfsfix /dev/sda1

Finally mount your partition.

Are you sure a valid NT file system is on /dev/sda1? Does it boot?

What you see in fdisk's output is the "partition ID" and "type", given when the disk is partitioned, no file system made yet. Only after an mkfs (or "format" in windows speak) a file system is available and recognized.