Windows 10: Why can't I combine disks to add more space to C:?

I have disc and disk 1 on my computer It won't let me upload a screenshot for some reason, it's in the reply belowC: is on disk 1 and is almost full. I have deleted everything from disk 0, it's now empty. I cannot figure out how to allocate the space to disk 1/C:

:)

 

Unallocated Space to C Drive

Thanks

 

Unallocated Space to C Drive

Hi Travis,

It appears that a disk partition was created but was never assigned its allocation. Assuming there are no files stored in the unallocated partition, perform these steps to combine it with your C: drive:

• In Disk Management, right-click on (C which appears next to the
  Unallocated partition.
  
• Select Extend.

Let us know if you're able to combine the spaces after following the steps above.

Regards.

 

Trying to combine disk space

My C:\ is starting to get really low on space so i want to combine my second hard drive D:\ which is more or less empty. I´ve been through Disk Management but the options "extend volume" that i want to use are greyed out.

I´ve tried formatting the empty drive that i want to combine with the C:\, I´ve tried partitioning it but nothing seems to be working.

I´ve included a screen shot so you can see what I´m looking at.

Thanks in advance