"Not enough disk space"

As the name suggests when I try to download any packs or updates it tells me I do not have enough disk space. however it says "amount required 17.6GB, amount available 984.6GB" so how dose nearly 10X the required disk space not enough? I am downloading it to the D drive not the stander ed C drive, however it is specified to download there and did not have a problem installing everything except visual studio support three days ago. I also have a local drive however when I download there I get the "no internet connection" error that is displayed instead of "not enough memory" I have checked every internet outage point and nothing. basically unity is being a huge brat right when i need it the most.