That 450MB partition is (or used to be) a System partition. Don't know why it has a 'name', but all you want to do is remove the drive letter.
Don't try to merge that into the C.
What I want to do is extend C, but I can only do this if D comes after C.
Is there a way?
Picture of your Disk Management window, please.
https://www.reddit.com/user/_AceX/comments/8jng1h/can_i_move_space_from_the_beginning_of_disk_to/
Best I can do; it won't let me use my imgur img here.
That 450MB partition is (or used to be) a System partition. Don't know why it has a 'name', but all you want to do is remove the drive letter.
Don't try to merge that into the C.