Yes, and there's no risk at all, except perhaps the ire of the Helpdesk and the rest of IT when they find you have trampled all over the partition.
Firstly, you can downsize the Windows partition by 30GB and still leave Windows in place as is, using gparted Partition | Resize from Linux; if you strip apps and data out of Windows by uninstalling programs and deleting data, you can downsize it further.
Then, resize /dev/sda3 after booting from a Live flash drive or a Live CD/DVD.
Now, if you want to complete nuke Windows, delete /dev/sda2 entirely. There may be a recovery partition in /dev/sda1 so I would leave that alone. Then, resize /dev/sda3 after booting from a Live flash drive or a Live CD/DVD.
Should there be a power blip while this is underway, GRUB2 (the current boot selection system) may be damaged, so just in case, this article explains how to revive it if needed.